Sunday, January 1, 2017

Wasps of Southern Oregon (2016)

Mischocyttarus flavitarsis ♀ eating honey.
At first mention of wasps, many people withdraw to a position of fear. Wasps can be intimidating to some, notably the notorious (infamous?) social wasps in the Vespidae (yellowjackets, hornets, and paper wasps). Yet, the vespid wasps only represent around five percent of total wasp species. The majority of the world's wasps remain unseen, some are too small to see with the naked eye (i.e. Mymaridae) while others are large enough to take down a tarantula (Pepsinae). Two of smallest flying insects in the world are parasitoid wasps in the genus Megaphragma (Trichogrammatidae) which are smaller than some amoebae, single celled organisms, and are parasitoids of the eggs of thrips which are themselves incredibly tiny (the smallest arthropods are 139 µm).
Polistes aurifer, a docile paper wasp which forms small nests
Wasps are incredibly diverse and fill many ecological roles. They are pollinators, predators, parasitoids, and also food for vertebrates including birds and reptiles (as well as feeding on each other, in some cases). Many of these attributes are overlooked, the deeds of a few of the eusocial stinging predatory wasps has a deep impact on the psyche of many people. The fear induced by the eusocial wasps is directly tied to their survival, the nests of paper wasps and similar colony forming wasps are full of precious brood and occasionally other resources that attract a myriad of predators, including but not limited to bears and birds. The venom produced by the eusocial wasps differs from the solitary wasps in its mode of action. The solitary wasps, even the very painful sting of the tarantula hawks (Pepsis spp.), has little to no lasting symptoms or damage after the pain subsides. Eusocial wasps, however, have venom that breaks down cell membranes and damages nerves, and with enough stings, can stop a heart from beating and kill. Not all wasps have stingers, while males of all hymenopterans lack stingers.
Ophion sp. (Ichneumonidae: Parasitica), a parasitoid wasp that uses caterpillars as hosts for its larvae.
The Hymenoptera is broken into three groups: Symphyta, Parasitica, and Aculeata. The first and most ancient of these is the Symphyta which contains the sawflies, horntails, and wood wasps (not pictured). It is believed that all other hymenopteran groups descended from this clade. The Symphyta do not have stingers, but an ovipositor used to bore holes and lay eggs in plant material (it is saw-like, thus sawfly). The Parasitica is comprised of true wasps (which have the characteristic constricted wasp waist) that do not have true stingers but ovipositors instead. Many are parasitoids or predatory in the larval stage, and all are solitary (do not form colonies). The last group, Aculeata, contains the most familiar and advanced members of the Hymenoptera: stinging (predatory) wasps, bees, and ants. Most have stingers but lack ovipositors, eggs are dropped out of a special opening at the tip of the abdomen under the stinger. One exception is the Chrysidoidea which, although belonging to the Aculeata, generally lack or have greatly reduced stingers and venom glands.
Philanthus crabroniformis ♀ flying towards Eriogonum compositum
As pollinators, wasps are highly underappreciated. Wasps visit many flowers in many plant families for nectar, their primary source of carbohydrates as adults. A few species also collect pollen though pollen collecting is mostly limited to pollen wasps (Masarinae, more like bees in their dietary habits than wasps). Most wasps prefer flowers with easily accessible floral rewards, such as EriogonumEricameria, Daucus, and Levisticum among many others. Australian orchids in the genus Drakaea are an example of plants that are strictly pollinated by wasps, specifically in the family Thynnidae (Vespoidea), by means of mimicry. Drakaea flowers resemble the flightless female wasps which the males attempt to carry to a secluded location to mate. Through several frustrating attempts, Drakaea orchids are pollinated and the duped males receive nothing for their efforts.
Eumenes verticalis, a solitary potter wasp that builds small urn-shaped nests to lay its eggs in.
I have observed a variety of plants that are visited by wasps. Most have easily accessible nectar as most wasps have relatively short proboscises. The majority of the wasps I've observed on flowers are predatory wasps (Aculeata) although parasitic wasps (Parasitica) are also known to visit flowers but are less frequently seen. The few parasitic wasps I've observed on flowers were an American pelecinid wasp (Pelecinus polyturator: Proctotrupoidea) on Daucus carota and a carrot wasp (Gasteruption sp.: Evanioidea), ironically, on Allium cepa. There are orchids which are primarily pollinated by parasitoid wasps, such as the Cryptostylis orchids whose only known pollinators are male wasps of the genus Lissopimpla (Ichneumonidae). Some wasps don't feed on nectar, instead some feed on honeydew (the frass of sap-sucking insects) or on the hemolymph (arthropod equivalent to blood) of hosts or prey. A few wasps (some Cynipoidea and Trichogrammatidae) don't feed at all in the adult stage, and only live long enough to mate and lay eggs.
The big hairy bee-hind of Bombus vosnesenskii (Apinae) foraging on Lathyrus latifolius. Branched hairs are what differentiate bees from wasps, a feature bees adapted to collect pollen as the primary source of protein for their larvae. Wasps are carnivorous in the larval stage (with the exception of pollen wasps and plant tissue feeders like the cynipid wasps).
Bees likely diverged from sphecid wasps in the early Cretaceous period (see Bees of Southern Oregon, Owen 2016), evolving branched hairs for collecting pollen. Wasps are traditionally carnivorous, and retained simple unbranched hairs. Thus, wasps are not as efficient as pollinators when compared to bees. However, insect-pollinated angiosperms have adapted pollen that is often slightly sticky which helps it adhere loosely to insect bodies. Additionally, flying insects collect a strong positive charge from flight, while plants (which are grounded, literally) have a weakly negative charge. When the positively charged flying insect contacts the negatively charged flower, pollen adheres to the insect with static electricity and the flower temporarily picks up a positive charge. This change of electric charge can also be detected by some pollinators, such as bees, who will avoid the positively charged flower until the negative charge is restored. A single grain of pollen placed on a receptive stigma is all that is required to produce a fertile seed, so efficiency may not be as important as frequency of flower visitation and flower constancy (when a pollinator forages on a single plant species rather than many different species).
Polistes aurifer nest, docile as can be.
It is unfortunate that wasps are so quickly dismissed as pests. Ironically, wasps contribute in a big way to our pest control efforts by preying on many other arthropods that are considered true pests. Predatory wasps are predators of the larvae of many insects from cutworms, to caterpillars, to wood boring beetle larvae and non insects like spiders. Parasitoid wasps, largely unseen, use hosts from nearly every insect order as well as non-insect arthropods, hosts such as mites, aphids, cockroaches, dragonflies, grasshoppers, thrips, barklice, and antlions to name a few. The pest control services of all insects in the United States is estimated to be around $4.5 billion considering the losses due to pests if the current services were ceased (Losey & Vaughan 2006). The Hymenoptera account for at least sixty percent of all insect predation on other insects (LaSalle & Gauld 1991), so it could be extrapolated that around $2.7 billion of annual pest control services can be attributed to the Hymenoptera.
Unidentified ichneumon wasp (October)

Below I have composed all the wasps I have been fortunate enough to photograph and identify this year in my Southwestern Oregon locale. They are arranged by one of several currently accepted (or nearly so) taxonomic interpretations. A fair warning, this is not an at all a comprehensive account of the wasps in my area, only the ones I have observed and photographed. The first section, Aculeata, is composed of the most familiar of the wasps: the stinging (or predatory) wasps which include the social wasps and also the bees (I have treated bees in a separate composition, see Bees of 2016). The following section, Parasitica, contains the parasitoid wasps which do not have stingers as the predatory wasps (Aculeata), although some are capable of poking and injecting venom. Lastly I have included ants, though technically they are considered to be a family within the Aculeata. Information of their life histories has been compiled from a variety of sources, found in the References at the end. I have also included many personal observations and speculation, if nothing else, for my own amusement. Please, enjoy:


Eumenes verticalis ♀
The Aculeata represents all the stinging Hymenoptera, the females of which have stingers but lack ovipositors, unlike the Parasitica which is comprised of parasitoid wasps which lack stingers but have functional ovipositors. Some species (many Chrysidoidea) have lost their stingers and evolved unique forms of ovipositors out of their abdominal segments rather than from the type of ovipositor found in the Parasitica (which evolved into the stingers of the Aculeata). Many in the Aculeata can fairly be called parasitoids or kleptoparasitoids (i.e. Chrysidoidea, Ampulicidae, etc.) as many use living hosts to raise their young unlike the typical predatory wasps in most genera. Eusociality, complete with divisions of labor and occasionally nonreproductive individuals such as what is found in honeybee colonies, is found exclusively in the Aculeata. This is the most advanced of the clades of the Hymenoptera, and far more is known about their biology than the of the many obscure wasps of the Parasitica.

Superfamily Apoidea

The Apoidea contains the bees (Anthophila) and many of the bees closest relatives: Ampulicidae, Sphecidae and Crabronidae. These non-bee groups contain predatory wasps such as the sand wasps (Bembicini) and mud daubers (Sceliphrini). Wasps capture prey from various insect orders to bring back to the nest, including cockroach nymphs, aphids, beetles, butterflies, and even bees and other wasps, as well as other arthropods like spiders. Some are kleptoparasitic and will steal prey from the nests of other wasps. Many nest in the ground, but still vary widely in their construction. Cockroach wasps (Ampulicidae) paralyze cockroach nymphs to drag back to the nest, much like pomplid wasps drag spiders, where an egg will be laid on it and the cell sealed. Once hatched, the larvae will feed on the still living, but paralyzed, roach nymph until it pupates.

Family Crabronidae

The Crabronidae is probably the most closely related family to the Apidae (bees), though it is entirely predatory. This group differs from the Sphecidae, which it was once included, most notably by the lack of a stalked petiole, or thread-waist found in many wasps, between the thorax and abdomen. Many are bee-like in appearance due to the short petiole, but have very little hair on their bodies and so appear more shiny than most bees.

Subfamily Philanthinae

The subfamily Philanthinae are predators of bees (in the tribe Philanthini), ants (tribe Aphilanthopini), or beetles (tribe Cercerini). They are often seen at flowers where adults drink nectar, and seek prey for their nests in some instances. There are many species in this group, one of the largest in the Crabronidae, and they all nest in the ground. They are all solitary, though they occasionally nest gregariously.

While the tribe Philanthini contains bee predators, they occasionally collect other wasps to provision their nests. The tribe Cercerini is particularly fond of weevils. The tribe Aphilanthopini are specialists who prey on ants. The genus Aphilanthops (Aphilanthopini) provision nests exclusively with winged queen ants in genus Formica. Often many prey insects are taken per cell, highly dependant on the size of the prey. For larger prey, less are needed.

Tribe Philanthini

The tribe Philanthini contains three genera: Philanthus, Prophilanthus, and Trachypus, although Philanthus is the most studied of these. The genus Philanthus contains about 135 species in the world with thirty two of them native to the United States and Canada. They dig one to several nests in sandy or hard packed alluvial soil each season, often over a period of a few weeks to a month, depending on the species. Each female excavates and provisions her own nest, though many nests may be found very close together where the substrate is suitable. A nest may have between four to fifteen separate cell chambers which branch off of a main tunnel. When a female completes and provisions one nest, she may go on to build more nests if she lives long enough.
Philanthus crabroniformis ♀ and a carpet beetle (Dermestidae) on Eriogonum compositum (June)
Philanthus spp. are known as beewolves, a common name which depicts their prey of choice. The types of bees hunted vary regionally and between species, although bees in the family Halictidae are most common, but other bees in the Colletidae, Andrenidae, Megachilidae, Anthophoridae, and Apidae are also occasionally hunted. Honeybees are more typical prey of larger Philanthus species such as P. bicinctus, P. crabroniformis, and P. sanbomii, as well as the European P. triangulum. Other wasps are occasionally captured and subdued as prey to be placed in a cell. Wasps in the families Scelionidae, Eumenidae, Masaridae, Sphecidae, Ichneumonidae, Braconidae, and Chrysididae have been found in the nests of various species of Philanthus.
Philanthus crabroniformis ♀ on Eriogonum compositum 
Beewolves pursue bees (or other wasps) which are in flight more often than when the prey are visiting flowers, although flower patches are the usual hunting grounds. Philanthus are heavily armored and resistant to stings from bees but are still occasionally killed in action. Prey are often stung quickly resulting in complete paralysis, ensuring "fresh meat" for the developing Philanthus larvae. Between six and twenty four prey items (individual bees or wasp prey, that is) are placed into each cell. The amount of prey items used in each cell probably depends on the size of both hunter and hunted. Once the last bee is placed in the cell, an egg is laid and the cell is sealed with a soil plug.
Philanthus crabroniformis ♀ on Eriogonum compositum
Male beewolves (not pictured) have large eyes which nearly touch at the top of their heads, much like the eyes of male honeybees (Apis mellifera ♂, also known as drones). Males are territorial, and mark their territory with volatile chemicals secreted from their head. The scent is spread onto the abdomen with specialized brushes on the head, and distributed on plant material by dragging the abdomen. When a trespasser is detected, a male will meet its opponent with head butting and grappling. Since they can't sting, males of some species will bite other males who enter their territory, although Philanthus crabroniformis isn't known to do so.
Philanthus crabroniformis on Croton setigerus (July)
I have encountered Philanthus crabroniformis twice, both times visiting flowers. Eriogonum compositum (Polygonaceae) is a relatively large clump forming perennial that grows in rocky places near waterways in my region (Southern Oregon). E. compositum has a generalist pollination strategy, attracting a wide range of pollinators with the exception of bees which were scarce during my observations despite being located near a large honeybee apiary. Croton setigerus (Euphorbiaceae) is a low growing annual herb which grows in fields and roadsides, often places with little competition and poor conditions. C. setigerus, too, appeared to have a generalist pollination strategy, although it attracted fewer insects than E. compositum. Halictid bees (Halictus ligatus) and the occasional honeybee were observed visiting the male flowers, while the odd ammophiline wasp was observed along with P. crabroniformis.

Family Sphecidae

Members of the family Sphecidae are commonly known as thread-waisted or sand wasps, delineating their morphology and nest biology. Contrary to the Crabronidae, sphecid wasps have a thin and elongated petiole (the waist). Most species nest in the ground in sparsely vegetated areas, but a few build mud nests above ground (the aptly-named mud daubers). A few species nest in hollow plant stems or abandoned bee tunnels in wood. They are solitary, and similar to the Crabronidae many mass provision nests with paralyzed arthropods (larval and adult) from various taxonomic orders including spiders (Araneae), grasshoppers (Orthoptera), beetle larvae (Coleoptera), and caterpillars or sawfly larvae (Lepidoptera or Hymenoptera) depending on the wasp species. Adult wasps feed on flower nectar, and will also feed on honeydew, extrafloral nectaries, and the hemolymph (arthropod blood) of their hosts. Some species place a single large prey item in a cell chamber, but the number of prey items depends on the size of the wasp and the size of the prey.

Subfamily Ammophilinae

The Ammophilinae are ground nesting wasps most commonly referred to as the thread-waisted wasps, although other families share this trait. Females excavate unbranched tunnels in sandy compacted soil with one to two cell chambers. Nests are provisioned with one large to many small moth caterpillars or sawfly larvae (similar in appearance to lepidopteran caterpillars) either all at once or progressively as the wasp larvae grows.
Ammophila sp. on Allium sphaerocephalon (June)
Ammophila spp. excavate nests with the use of their mandibles and legs, often taking the excavated soil away from the nest entrance. A female will first dig a nest then use a pebble and sand to conceal the entrance before embarking on the task of finding a caterpillar host. Once paralyzing a host and returning to the nest, she will reopen the nest and drag the caterpillar inside. Once enough hosts are delivered into the nest, or a single large caterpillar host is delivered, the female will lay an egg and seal the nest again with a pebble and cover it in sand to hide it. If the host caterpillar is large, the female wasp will be unable to fly with it and must drag the prey back to the nest, occasionally at incredible distances from the nest site. How they can find their way back to the nest whilst dragging their prey is a mystery. It would be similar to taking a plane from a house you just moved into and then walking backwards back home.
Ammophila sp. on Allium sphaerocephalon (June)
Adult Ammophila wasps feed on flower nectar, and so are often found visiting flowers. I have seen them on a variety of flowers including various alliums (Allium spp.), Croton setigerus, and various mint relatives (e.g. Origanum spp.). I would assume they have excellent eyesight as they have made themselves very difficult for me to get a satisfactory photograph.

Subfamily Sceliphrinae

Nearly 150 species in six genera around the world and seven species in three genera north of Mexico make up the subfamily Sceliphrinae. Wasps in this subfamily live in a diversity of nest types including exposed mud nests (Sceliphron spp.) or preexisting holes in wood (Chalybion spp.). Prey are paralysed with one or more stings then sealed in the nest for the larvae to feed on. One to twenty or more prey items are placed in cells depending on the size of the prey. Prey includes spiders or cockroaches (Podium spp.).

Tribe Sceliphrini

Sceliphron caementarium (August)
The black and yellow mud dauber (Sceliphron caementarium) is a common species of solitary wasp.  They are large wasps, over an inch long (~28mm) with a thin and highly elongated petiole. Though they may appear daunting, stings by mud daubers is uncommon. The sting is usually reserved for subduing and paralyzing hosts for their offspring: spiders. Spiders in many families have been found in mud dauber nests including the families Anyphaenidae, Oxyopidae, Salticidae, and Thomisidae. They have a marked preference for orb weavers, Araneidae, whose stationary lifestyle may facilitate a relatively easy capture. The female wasp lays an egg on the first spider to be placed in a cell, then continues to place up to twenty five or more spiders inside until the cell is full. The wasp larva begins feeding on the organs and other internal structures of the spiders before eating the rest of the body. The spider provisions are consumed within two to three weeks. I've often found a few dessicated spider remains inside the cells, even after the wasps have built their pupal case.
Sceliphron caementarium nest is composed of layers of mud.
The nests of S. caementarium are the most conspicuous sign of their presence, being made of locally sourced mud and adhered to a variety of locations, some of which highly visible. Nests start as a single tube-like cell, then more cells are added. Sceliphron requires a source of mud nearby, in contrast to related genera that bring water to mineral soil to make their own mud for nest building. Once all the cells are provisioned and sealed, the mother wasp covers the entire structure in a thick second layer of mud. The mud served to protect the larvae from parasites and predators, as well as to regulate the conditions inside (protect from frost, etc.).
Sceliphron caementarium nest variation
There is great variation among nest shape and sizes. Some nests I've found are just a single capped cell while others may be several inches long and have two dozen cells. The type of mud available determines the color of the nest, and to an extent the shape and texture as different forms of mud have different working properties.
Sceliphron caementarium pupal case with prepupae within
There may be one to a few generations per year, but the last generation appears to enter a state of diapause in the prepupal state after building the pupal case. The case, or puparium, is spun from a fine silk-like material and forms a soft cellophane-like shell that protects the prepupae from excessive moisture and pests. The case itself is suspended within the mud cell, sometimes with the dessicated remains of a few spiders.
Contents of Sceliphron caementarium nest with prepupae (within and without puparium, left) and a cuckoo wasp (Chrysididae) adult and prepupal case (right).
Nests of Sceliphron caementarium are often targeted by parasites or are subject to damage from microbial life such as mold or fungi which seem to destroy the viability of individual cells. Interestingly, within a single nest, some of the individual cells may be subjected to various maladies while others may remain healthy and viable. When dissecting a nest in early winter, I discovered a green metallic cuckoo wasp (Chrysididae, see below) dead in one of the cells. Several of the cells also had an immature chrysidid prepupa in a light cream-colored pupal casing instead of the elongated amber-colored pupal casing of Sceliphron. 

Superfamily Chrysidoidea

The Chrysidoidea, often called cuckoo wasps, are a unique group of parasitoids and kleptoparasites within the Aculeata. The lives of some are nearly identical to the parasitoid wasps in the Parasitica though they differ in that they had developed stingers (like all aculeate wasps) from the parasitican ovipositor. Some, however, lack functional stingers (or have stingers that are much reduced) and have highly reduced venom reservoirs. Obversely, some chrysidoids (i.e. Bethylidae) are said to have a painful sting while others have enlarged venom glands.

While some, such as the Chrysididae, are kleptoparasites which lay their eggs in the nests of other bees or wasps, the rest could fairly be called parasitoids. Hosts vary considerably between families. The Embolemidae are poorly understood and little is known about their biology, although they have been reared from Achilidae (planthopper) nymphs, and also found in subterranean nests of ants and mammals. Sclerogibbidae are ectoparasitoids of nymphal Embiidina (webspinners), though once again their biology is poorly known.

The Dryinidae use hosts in the Auchenorrhyncha (leafhoppers, treehoppers, and spittlebugs). Female drynids are wingless and have pincer-like chelae on their front legs that are used to grab onto host insects. When a host is captured, she stings it to temporarily paralyze it. Occasionally the host is eaten (and thus killed) but other times the female will deposit an egg within the leafhopper through the soft membrane between bodily segments. The larvae are usually endoparasitic in the beginning of their lifecycle then gradually becoming ectoparasitic, attached to and feeding on the host from the outside. One species of drynid, Crovettia theliae, is completely endoparasitic and also polyembryonic with a single egg developing into up to fifty genetically identical offspring. Similar to the Dryinidae, Bethylidae are parasitoids of lepidopteran (Bethylinae) and coleopteran larvae and pupae (Epyrinae and Pristocerinae).

Family Chrysididae

The Chrysididae, or cuckoo wasps, are not easily mistaken for other wasps. They are usually a metallic green or blue, occasionally with metallic red on the abdomen or parts of the thorax. They are heavily armored, an adaptation that allows them to enter the nests of other hymenoptera. This family contains both parasitoid and kleptoparasitic species (the lifestyles of the latter give rise to the common name, much like cuckoo birds). Kleptoparasitic species lay eggs in the nests of sphecid wasps (such as Sceliphron spp.), as seen in the photo above, and eat the provisions within the nest of the host insect. Parasitic species are ectoparasitoids of the larvae of various bees, sphecid wasps (Sphecidae), potter wasps (Eumenidae), or more rarely, the larvae of sawflies or the eggs of stick insects.

In many cases the females have highly reduced stingers and venom glands, though there is at least one species with a prominent stinger and venom glands that are large even compared to other Hymenoptera. The Chrysididae have ovipositors, but they are distinct than the ones found in the Parasitica and unique in the Aculeata. Chrysidid ovipositors evolved independently from the aculeate stinger into a telescoping egg-laying apparatus that can withdraw into the abdomen. The ovipositor is used to lay the egg into the nest or pupal case of the host insect.

Subfamily Chrysidinae

Forty four genera in three tribes constitutes the subfamily Chrysidinae. The tribe Chrysidini is by far the largest with nearly half of the species. The Elampini tribe is the nest largest, while the Parnopini is very small with only three genera worldwide. Parnopine wasps prefer arid habitats and use sand wasps (Bembicinae) as hosts. Entry is gained into the nest or puparium of the host by chewing a hole, followed by the deposition of a single egg, then finalizing the process by sealing the hole with debris and saliva, usually of the same material as the structure was originally created.

Tribe Chrysidini

Chrysis angolensis, found dead in a nest of Sceliphron caementarium
Chrysis angolensis is an Old World species that is thought to have been introduced into the United States during or after World War II. They are nest parasitoids of the prepupae of sphecid and crabronid wasps (particularly Sceliphron caementarium). This specimen was found dead in a mud nest of S. caementarium, and is the same individual seen in the previous photo. I had also discovered a number of pupal sacs which most likely belonged to this species. They are a metallic green, but depending on where the light hits it can make it appear blue. This cuckoo wasp probably gained access to the cells with her mandibles to lay her eggs, then sealed the nest again with saliva and debris created when creating the opening.

Tribe Elampini

Omalus sp.? (October)
The tribe Elampini contains around twenty genera of very small chrysidids. They all use other Hymenoptera as hosts, particularly ground nesting wasps in the Crabronidae. Omalus spp. use aphid wasps (Pemphredoninae) as hosts, though other ground nesting wasps are recorded hosts of other elampines such as Hoplisoides spp., Solierella spp., and Tachysphex spp. Old World elampines are also known to use bee hosts in the Halictidae and Megachilidae as well as crabronid wasps.
Omalus sp.? (October)
I watched this tiny wasp scuttling about on my porch stairway, continuously antennating the wood. At first I nearly mistook it for a small dipteran, though a closer look revealed otherwise. This tiny wasp was no longer than around one eighth of an inch (or around three to four millimeters long).

Superfamily Pompiloidea

The superfamily Pompiloidea is probably best known for the spider wasps, Pompilidae, and the so called velvet ants (or "cow killers"), in the family Mutillidae. Most are ectoparasitoids (or occasionally kleptoparasites) of immature Hymenoptera or paralyzed adult spider hosts. Rarely, other insect orders are used as hosts.

Female velvet ants (Mutillidae) are conspicuous at times since they are wingless and meander along the ground searching for hosts or host nests. While the Pompilidae always use spider hosts, the Mutillidae use a variety of hosts from (usually) ground nesting bee and wasp larvae as well as (though rarely) immature stages of flies, slug moths (Limacodidae), beetles, and cockroaches. Female mutillids are the most often encountered, while males are less frequently seen. Unlike the females, the males are winged. Both will visit flowers for nectar, but also feed on honeydew and occasionally females will feed on host insects. Mutillidae differ from other wasps in the Pompiloidea by being very densely hairy and often brightly colored (usually red).

Lesser known and less common families are the Sapygidae and Myrmosidae wasps. Sapygid wasps are parasitoids or kleptoparasites of other aculeate larvae and are particularly fond of twig-nesting Megachilidae bees. Myrmosid wasps are parasitoids of the larval stages of various solitary bees and wasps, and have wingless females. Both of these families are easily distinguished from the Mutillidae since their bodies appear nearly hairless.

Family Pompilidae

The spider wasps are some of the most well known of the solitary wasps. They are also unique among the Pompiloidea in that they always use adult spiders as hosts, either in the spiders own den or in a nest they excavate themselves. Many pompilids seem to use specific genera as hosts. In any case, when a spider is found the wasp will entice it to exit its den and grapple with it until it can sting the spider. Sometimes repeated stings are necessary but paralysis is always permanent. Once dragging the spider back into its den or to a specially dug nest, the pompilid lays a single egg on or near the spider and seals the nest. The pompilid larvae will feed on the living spider until it pupates and emerges the following year. Some sphecid wasps, such as the Sceliphrinae, also use spiders as hosts, but the nests of sceliphrines are aerial while those of most pompilids are subterranean.

Subfamily Pepsinae

With 2000 species in over sixty genera worldwide, the most well known of the Pepsinae are the [relatively] massive tarantula hawks in the genus Pepsis. Tarantula hawks are typically large wasps, some with metallic blue hues and often with orange wings. The largest are up to two inches long, and have the most painful sting of any Aculeate wasp, second only to the bullet ant (Paraponera clavata). Pepsis spp. are more common in arid regions of the American Southwest, but other species ranges extend up to Canada. Most visit flowers, and some are considered important pollinators. Pepsinae appear to specialize in hunting spiders in the Mygalomorphae which includes tarantulas and trapdoor spiders.

Tribe Pepsini

Calopompilus pyrrhomelas (September)
Calopompilus spp. are not quite as large as their Southern cousins, but they do reach about an inch in length which is still large as far as solitary wasps are concerned. C. pyrrhomelas specializes in the folding door spiders in the genus Antrodiaetus. When spiders are paralyzed, they are sealed inside their own den along with an egg. Adult Calopompilus aren't known to frequently visit flowers, but they have been observed visiting rabbitbrush (Ericameria nauseosa) for nectar.
Calopompilus pyrrhomelas (September)
Unfortunately, this individual was found dead in a pool of water. Fortunately, I was able to collect it and I still have it for future study (and because I think it is really really cool). I may not have ever encountered this species this year if it had not drowned. Having found this single specimen suggests that there are more of them.

Subfamily Pompilinae

The subfamily Pompilinae constitutes the largest subfamily in America north of Mexico. The majority of these wasps are completely black, with translucent to dark wings. A few exceptions are Tachypompilus species which are mostly red and Poecilopompilus which are mostly yellow. Most hunt spiders then bring them to a suitable location for excavating a nest, with the exception of the tribe Aporini which hunt subterranean spiders and use the spider's own burrow to rear their young. In either case an egg is glued to the abdomen and the nest sealed. Prey varies widely, from orb weavers (Araneidae) to wolf spiders (Lycosidae), and there have even been reports of harvestmen (order Opiliones) being used. In fact, spiders from at least fifty genera in fifteen families have been recorded as hosts for Pompilinae wasps.

Adults often visit floral or extrafloral nectaries for sustenance, or sometimes seek out honeydew from sap sucking insects. Some species feed on the hemolymph of spider prey, occasionally hunting prey solely for the purpose of feeding on it. This kind of feeding has been demonstrated to improve egg laying and longevity for some wasps.

Tribe Pompilini

Arachnospila sp.? (September)
This spider wasp, and others like it, was seen exploring the outside of an active beehive. It is unclear what its intentions were, though there is a possibility that the scent of honey could have attracted it as many other insects are attracted. Spiders are also very common residents of the undersides of these particular hives, so it is possible this wasp was actively hunting. It disappeared under the lip of the lid shortly after this photo was taken.

Due to the similarity of features between many of the Pompilinae wasps, identification is not simple or easy. Features are probably best examined under a microscope by an expert, which I am not, rather than from inspection of a photo. Nevertheless, much of the information presented here remains the same.

Superfamily Vespoidea

Vespula pensylvanica (left) and Polistes dominula ♂ (right) eating sugar
This superfamily is best known for the social members, particularly paper wasps (i.e. Polistes spp.), yellowjackets (i.e. Vespula spp.), and hornets (Vespa spp.), although there are also many solitary species and obscure rarely encountered species. This superfamily was once considered to contain

While many of the social species are considered to be predatory, there are also parasitoid species which utilize a living host. One mysterious family with no common name, the Rhopalosomatidae, contains a total of four genera worldwide. Wasps in the Rhopalosomatidae, or alternatively rhopalosomatids (the closest we can get to a common name), are ectoparasitoids of cricket nymphs in the subfamily Hapithinae and are thought to be nocturnal.

Family Vespidae

The Vespidae are a large and familiar family with over three hundred species in at least thirty five genera of both solitary, semi-social, and eusocial wasps. The subfamilies Eumeninae, Euparagiinae, and Masarinae are all solitary, Stenogastrinae contains both solitary and social species, Polistinae are mostly semi-social, and Vespinae are completely eusocial. Euparagiinae are very rare and live in arid regions of southwestern United States. Pollen wasps, subfamily Masarinae, provision their nests with pollen rather than insects.

Nest materials vary from paper (plant pulp and saliva) as in the Vespinae and Polistinae to mud (i.e. Eumeninae, Masarinae) to preexisting cavities in wood, the ground, or old nests of other wasps (such as the old mud nests of Sceliphron caementarium). Prey varies as well, and with the exception of the Masarinae they all have carnivorous larvae. Prey are usually larval stages of Lepidoptera but other Hymenoptera are sometimes hunted as well as various life stages of many different types of insects. The Eusocial species seem to display the most diverse dietary habits, and will even take carrion or attack larger adult insects and return it to the nest in small pieces.

Subfamily Eumeninae

I have only encountered one family of solitary vespids, the Eumeninae. Most species, known as mason wasps, nest in preexisting cavities in wood, hollow stems, or in rock crevices, and use mud or sand to partition cells. Some species nest in the ground (all Pterocheilus, Odynerus, and some Euodynerus), and occasionally species build small mud turrets over the nest entrance (i.e. Odynerus dilectus, Euodynerus annulatus). Other species, known as potter wasps, build free standing mud nests (Eumenes and Zeta). Host insects, normally moth larvae but occasionally leaf-feeding beetle larvae, are paralyzed and sealed in the nest cells to be consumed by the wasp larvae. Adults of some species feed directly on the host's hemolymph, and a few eat entire portions of the host's body itself. Kleptoparasites and parasitoids often prey on eumenine nests, chrysidid wasps, mutillid wasps, and sarcophagid flies being the most common of these.
Eumenes verticalis ♀ (October)
Potter wasps are similar in appearance to their eusocial relatives (Vespinae) though they have a unique form, notably the unique shape of the abdomen. I found this female feeding on the nectar of rabbitbrush (Ericameria nauseosa) for at least the duration of my observation, perhaps twenty minutes.
Eumenes sp. nest
Potter wasps themselves are about as recognizable as their nests. Mud nests are attached to plant stems, trees, or sometimes other things like under pallets or other protective structures. The opening is smaller than the wasp itself, and the egg is laid once nest is complete by the female wasp sticking her abdomen through the opening. Normally a single caterpillar is used as a host, paralyzed, and stuffed into the nest and sealed. Unlike sphecid wasps, Eumenes does not need a source of mud nearby and instead can make their own mud by bringing water to mineral soil.
Eumenes sp. prepupae removed from a nest
By autumn, Eumenes larvae have reached the prepupal state (having consumed most of the host) and enter a state of diapause for the winter. The inside of the mud nest is coated with a cellophane-like secretion which serves to strengthen the thin mud walls and may also give it some resistance to water. Most nests are attached in protected locations such as under rocky overhangs or on plant stems.
Ancistrocerus sp. on rabbitbrush (October)
Ancistrocerus, along with Stenodynerus and a number of other genera, are collectively known as mason wasps rather than potter wasps since they use mud or sand to partition cells in tunnels in plant stems, wood, cracks in wood, or in subterranean excavations. Nests are sometimes made in preexisting excavations from other insects, or are even occasionally stolen from bees or other wasps. Some species build small mud turrets at the nest entrance, this is restricted to species which nest in the ground. I have even found old drawn comb of honeybees with mason wasp larvae inside, capped and lined with mud.
Stenodynerus sp. on Levisticum officinale (June)
Stenodynerus is the largest genus north of Mexico with forty eight species. Ancistrocerus has thirty one described species, seventeen in North America. All mason wasps mass provision their nests with caterpillars. They enter winter as prepupae and pupate in the spring.

Subfamily Polistinae

Polistes aurifer
The Polistinae has some familiar members, namely the paper wasps whose nests are typically composed of exposed paper cells in cavities or under overhangs. The common name, paper wasp, is a misleading term since wasps in the Vespinae also have paper nests. Unlike the Vespinae, Polistes and Mischocyttarus have no true worker castes, and all females are fertile (so technically there is no queen, per se). To keep order, there is normally a dominant laying female who will destroy the eggs of "rogue" layers. Brachygastra, however, exhibits complete eusociality with multiple queens in large paper nests and a sterile worker caste.

Similar to other eusocial or semi-social Hymenoptera in the United States, only newly mated females survive over the winter where it is cold. Females find a protected location, such as in a wood pile, to wait out the winter. Upon the onset of spring, females (or foundresses) build small hanging nests under eaves or other protected locations. Paper wasps typically prey on caterpillars but they may take larvae of other insects as well. The reason caterpillars are most often hunted is probably proportionate to their level of exposure and abundance compared to the larvae of other insects. Adults also feed on nectar, and in the genus Brachygastra nectar is brought to the nest and made into honey (thus their common name, honey wasps).
Nests of Polistes and related genera are parasitized by gregarious ichneumonid wasps in the genus Pachysomoides. Moths in the genus Chalcoela (Crambidae) are parasitoids of Polistes and Mischocyttarus nests. Chalcoela caterpillars feed on the wasp larvae, which I find to be ironic.
Mischocyttarus flavitarsis ♀ (October)
Mischocyttarus is very similar to Polistes except for the elongates and distinctively curved petiole. It is known as the Western paper wasp due to its westerly distribution. I spotted this female while working some beehives, honey had gotten onto the lid of an adjacent hive and she was feeding on the honey. Paper wasps aren't interested in hunting honeybees, but they have been known to rob hives of their resources. Another interesting adaptation I have observed is the ability for some paper wasps, particularly those with very long legs, to land directly on still water. Surface tension allows them to alight, drink, and take off without drowning.
Mischocyttarus flavitarsis ♂ (November)
A male Mischocyttarus on my finger. Males of many vespid wasps can be identified by their curled antennae. The green eyes are also distinctive from females, and the faces of some species are unmarked yellow. Males have no stinger, so there is no risk when holding one.
Polistes aurifer ♀ (November)
A female Polistes aurifer, known as the golden paper wasp, on my finger. I found this female hiding on some empty beekeeping equipment, her winter shelter. She was cold, moving slowly, and she let me photograph her for a while. Although she has a stinger and was fully capable of stinging me, I gave her little incentive to do so. Note that she is holding me, not the other way around.
Polistes aurifer ♀ (July)
While working in one of the apiaries this year, I had discovered a nest underneath some empty bee equipment. There were two or three workers who fled while the dominant female was unwilling to leave. While I had my beekeeping veil on, I decided to get some photos. I question whether or not I even needed a veil since there were no signs of aggression. She appeared to be missing part of her right forelimb, possibly in a battle for dominance with another female. Body size seems to be a determining factor with nest dominance, a result of good nutrition. Well fed larvae grow up to become larger adults, and larger adults can defeat smaller opponents.
Polistes aurifer eggs (July)
Nests of all paper wasps are made from plant and wood fibers held together with saliva, but they appear to use whatever is available including construction paper or even money. Unlike honeybees, many of the social vespid wasps (at least American species) build horizontal comb with the cells facing down. Paper wasps typically build a single rounded comb.
Polistes aurifer ♂ on rabbitbrush (October)
Males are produced towards the end of summer or the beginning of fall. They will mate with new females once and die. Like the Mischocyttarus male, the face is completely yellow with antennae that curl slightly at the tip.
Comparison between Polistes aurifer (L) and P. dominula (R), not to scale.
A common European invader in much of the United States, the European paper wasp (Polistes dominula, pictured above on the right) is slightly smaller than P. aurifer (photos not to scale). This species is slightly more aggressive, and often shares habitat with P. aurifer (which in my case is under the eves of my roof). They can be told apart by their patterns, higher contrasting patterns of P. dominula while the abdomen of P. aurifer is mostly a dull yellow. I would also like to add the observation that the antennae differ in color, P. aurifer antennae fade to black at the ends while P. dominula antennae are black at the base. The yellow markings on the thorax of P. dominula are also diagnostic.

Polistes dominula ♀, missing her right forelimb. (October)
The European paper wasp is native to Europe and parts of Asia and Africa and was first recorded in North America in 1981. It has been a highly successful colonizer and it expanded its range in the eastern and midwestern USA in the twenty years following its introduction. As an invasive species, Polistes dominula directly competes with native paper wasps, P. aurifer and Mischocyttarus flavitarsis. P. dominula establishes colonies earlier than the native species, and can thus get a head start on finding the most suitable nesting sites. Smaller body sizes than the native species, coupled with their preference for small holes and voids allows them to nest in a greater variety of nest sites than the larger bodied native species. Old or empty nests left over from the previous year may be reused by P. dominula, while native species do not. While the native species are primarily caterpillar hunters, European paper wasps may hunt a variety of insect types from many orders, including the larvae of other wasps or even other paper wasp nests.
Polistes dominula ♂ on my hand, males are incapable of stinging yet he did poop on me. (October)
Male P. dominula wasps have the conspicuously curled antennae and mostly yellow face. Like all the other eusocial or semi-social vespid wasps, they are produced in late summer or early fall to mate with new females who will overwinter and form new colonies in the spring.
Polistes dominula ♀ (October)
Some, but not all, Polistes wasps use a form of facial recognition to communicate with nestmates and understand hierarchy. Species with less descript facial patterns do not communicate this way, and instead have comparatively larger olfactory sensors. P. dominula and P. fuscatus are two that have demonstrated facial recognition of nestmates. There is also some speculation that they can recognize the faces of people, though I could not find anything to substantiate this.

Subfamily Vespinae

The subfamily Vespinae contains the most infamous of the social wasps: yellowjackets and hornets. They are markedly more aggressive and protective than other wasps, and their preference for nesting in trees and cavities (subterranean or otherwise) often places them near people. Nests of many yellowjackets and hornets can become very large, excessively large where winters are mild and colonies can perennialize. They are truly eusocial, having distinct castes complete with reproductive (queen, drone) and worker (sterile female) castes.

Much of the bad press comes from this group of wasps. They are also the most likely to turn up at a picnic or barbeque. Nest sites often overlap with human activity. In these ways they often interact with people. If a nest is approached or accidentally disturbed (such as mowing the grass and being unaware that a yellowjacket nest is underfoot), the unsuspecting human is met with an aggressive or at the very least intimidating response. This is bad for obvious reasons, but this is in fact how these creatures have been able to survive for millions of years. A colony is full of delicious treats, particularly if you are a bear (or one of a number of other mammals), and the highly aggressive response is their best means of defense only second to their typically hidden or inaccessible nest sites.
Vespula pensylvanica queen feeding on nectar from plum blossoms. (March)
Yellowjackets are one of the most commonly encountered social wasps in the United States. In the South they can form massive colonies, both above- and below ground, since they can perennialize through the mild winters. In temperate America, they form annual (occasional perennial) subterranean colonies. Newly mated queens are the only ones to survive cold winters, similar to the paper wasps (Polistinae). Upon emergence in the spring, they seek nest sites and feed on nectar from flowers. Surely they contribute to pollination, some species are quite hairy and fully capable of inadvertently spreading pollen.

Similar to honeybees, yellowjackets (Vespula spp.) utilize pheromones as one means of communication. Queen yellowjackets produce pheromones that induce sterility in the female worker caste, preserving her ability to preserve the queens genetic lineage. Another result of yellowjacket queen pheromone enables workers to recognize her eggs versus the eggs laid by workers. Laying worker eggs are destroyed or eaten.
Vespula pensylvanica ♂ (October)
Male yellowjackets have the distinctive and highly elongated antennae. They are likely used to search for virgin queens to mate with. Yellowjacket drones are produced late in the year, early autumn or late summer. Similar to honeybee drones, they mate once and die, their genitals torn from their body resulting in death.
Vespula pensylvanica worker (August)
Yellowjacket workers are the workhorses of the colony. Yellowjackets are omnivorous, as adults may feed on flowers, but carnivorous as larvae. Yellowjackets feed on a variety of other creatures, from insects of many orders to carrion to hamburgers. They will attack insects much larger than themselves and bring it back in small chunks to feed to their young. They will also rob resources from honeybee hives, much to the detriment of the hives and the beekeeper. In my experience, a strong hive should adequately fend off even the largest of yellowjacket populations while small colonies may be in trouble.
Vespula pensylvanica devouring a honeybee (August)
Yellowjackets are a major pest in an apiary. They will attack honeybees in the air or go right into the hive to attack them. They may also play a role as scavengers, bringing home bees which have died of other causes. In my experience, keeping one's hives at their peak health and utilizing reduced entrances can go a long way in mitigating the issue of yellowjackets.
Dolichovespula maculata ♀
Bald-faced hornets, technically a species of aerial yellowjacket, form large watermelon-sized nests which hang from the branches of trees. Their nests are composed of multiple levels of horizontal paper combs with an outer shell composed of many sheets of paper. The stereotypical image of a beehive hanging from a tree branch is more typical of the nest of Dolichovespula maculata.
Dolichovespula maculata 
These are large wasps, and create colonies with seven hundred or more individuals. They have diets similar to yellowjackets (Vespula spp.) and also commonly hunt honeybees where both are common. Honeybees are smaller, but have various defensive strategies to fend off or fight larger foes. When stinging doesn't work, they will form a tight ball of many individual bees around an attacker and vibrate their bodies to heat it up. So much heat is generated that they kill the attacker. This was probably the case with this individual. It is dead, and I found it fully intact at the bottom of a beehive earlier this year.
Dolichovespula maculata ♂ with Apis mellifera forager (October)
Similar to all other social vespid wasps, males are produced in the fall. Males were a common sight in October. I was working some hives when this male (note the curled antennae) landed on my glove. A worker honeybee landed next to him to investigate, then departed after losing interest.


Parasitoid wasp (Lissonota sp.) with a long ovipositor used for penetrating hosts and laying eggs.
The Parasitica is composed largely of obscure, rarely encountered solitary wasps that use
(usually) living hosts to raise their young. The primary distinction between the Aculeata and the Parasitica is the evolution of a stinger from an ovipositor. The Aculeata evolved from the Parasitica, it is believed, and lost the use of their ovipositor for laying eggs in exchange for a stinger capable of stinging and injecting venom. For the Aculeata, eggs are dropped from an opening at the tip of the abdomen under the stinger. The Parasitica, however, deliver eggs with an ovipositor. Some have relatively short ovipositors, while others have very long ovipositors capable of penetrating solid wood when seeking wood-boring hosts or penetrating soil when seeking soil dwelling hosts. Venom is usually injected along with the eggs, and despite lacking true stingers some parasitoids are capable of using their ovipositor to sting people, though this probably requires provocation as I have discovered these creatures are very quick to flee.

Hosts vary considerably, in nearly every insect order and even other arthropods such as spiders and mites. Eggs, larvae, prepupae, pupae, and adult hosts are used depending on the species of parasitoid wasp. Some wasps use plants as hosts, such as gall wasps (i.e. some Chalcidoidea and all Cynipoidea). Eggs can be laid near, on, or within a host, and larval development can take place on or within a host at different stages depending on the species. Some members of the Parasitica are known as hyperparasitoids, those which attack the parasitoid larvae within another host (thus unintentionally saving the original host in some cases).

Polyembryonic parasitoids are those that lay one egg inside a host which develops into many larvae, and depending on the species many wasp larvae can emerge from a single egg laid, or even a few thousand in the genus Copidosoma! The eggs of polyembryonic species occasionally divide within a host or there may be multiple embryos within a single egg. Many other fascinating scenarios take place, far beyond my scope of knowledge. To read more about the Parasitica I suggest these books: Bees, Wasps, and Ants by Eric Grissel (Timber Press 2010), Parasitic Wasps by Donald L. J. Quicke (Springer 1997), and Solitary Wasps by Kevin M. O'Neill (Comstock Publishing 2000).

Superfamily Chalcidoidea

The Chalcidoidea is a large and varied group of small wasps with an incredibly diverse array of lifestyles. There are well over 500,000 species described worldwide, and over 2,000 in the United States alone. Most are parasitoids of insects and arachnids, yet some are plant tissue feeders who grow up within stems, leaves, seeds, or flowers, or even make galls. Fig wasps, family Agaonidae, develop and mate entirely within figs. Some are parasitoids of pest insects (within the orders Lepidoptera, Diptera, Coleoptera, and Hemiptera) and are used for pest control purposes. At least one species, Tetramesa romana (Eurytomidae), has been released into the US to control an invasive grass, Arundo donax (Poaceae).

The smallest wasps, and smallest insects, are in the families Mymaridae and Trichogrammatidae, both contain egg parasitoids of very small host insects: Thysanoptera (thrips) and Psocoptera (barklice). The most peculiar species, however, are those which are hyperparasitic and use other parasitoids as hosts. This can be in the form of secondary or tertiary parasitoids, or to the extreme as quaternary parasitoids. This equates to a parasitoid parasitizing a parasitoid parasitizing a parasitoid of some sort of unfortunate host. It is fathomable that such an interaction may even save the original host, but only if the secondary parasitoid parasitizes the primary parasitoid before pupation, the point at which the original host would be severely weakened by the primary parasitoid. Crystal clear, right? Other species may be polyembryonic.

In all, chalcid wasps attack insects in around 340 families representing fifteen orders, as well as some arachnids (i.e. pseudoscorpions, ticks, and mites). Mostly immature stages of hosts are parasitized, but adult hosts are sometimes utilized as well as eggs and egg sacs (including spider egg sacs, in some cases).
Chalcid wasps hovering around Quercus kelloggii (April)

I took this photo to capture the light shining through the new growth of the California black oak, and only later did I discover the wasps. Expert identification suggested Chalcidoidea, though there is no way to be sure so allow me to speculate. Oak trees are host to many insects, including many species of moths which may play the role as hosts to countless species of parasitoid wasps. Gall wasps, Cynipoidea, are also found to associate with oaks in abundance. All of these insects are possible hosts for chalcid wasps, depending on the species.

Superfamily Cynipoidea

Gall wasps, Cynipoidea, are a unique group of parasitoids because most feed on plant tissue. Some are gall inquilines, those that live within the galls of other Cynipoidea though don't create galls themselves. Families Figitidae and Ibaliidae are parasitoids or hyperparasitoids of other insects. Figitidae wasps are parasitoids of various Diptera, Neuroptera, or are parasitoids of various gall inducing wasps in the Cynipoidea and Chalcidoidea (i.e. Cynipidae, Eurytomidae). Some Figitidae are hyperparasitoids of Braconidae or Chalcidoidea parasitoids of Hemiptera hosts. The Ibaliidae are parasitoids of sawflies in the family Siricidae. Early Ibaliidae instar larvae are endoparasitic, but later instars emerge and eat the rest of the host from the outside. The Cynipidae is made up entirely of gall inducing wasps and gall inquilines, and nearly entirely phytophagous (feed on plant tissue).

Family Cynipidae

The family Cynipidae is an oddity in the world of wasps (though if you have read this far, it has probably come to light that wasps, particularly the Parasitica, are an oddity as a whole). Cynipid wasps are mostly gall forming, phytophagous (herbivorous) wasps which induce galls in which to feed on and live within during their development. Inquilines don't make galls themselves, but feed on the gall of another wasp, occasionally killing the host larvae.

Gall forming wasps initiate the formation of a gall when certain chemicals excreted by the wasps make contact with the plant tissue, though the exact mechanism is unknown in most cases. The type of plant or tree as well as the location of the gall is very specific to the species of wasp. Most gall wasps only form galls on a select few or single species on plant or tree. Usually oaks (Quercus spp.) and other trees of the family Fagaceae, or roses (Rosa spp.) are most often used as host plants for gall formation. There are some herbaceous gall formers who favor plants in the families Asteraceae, Lamiaceae, and Papaveraceae, though their galls are less conspicuous.

The gall serves two primary purposes for the wasps: as a source of food for developing larvae and to protect the immature wasp from its natural enemies. The inside of the gall is full of nutritious plant tissue, and a source of protein for the wasp larvae. The outside of the gall is often hardened to form a shell-like exterior. Sometimes the outer layers are toxic, a protective measure that keeps predators from eating the gall.

There are at least fourteen hundred described species of cynipid wasps in the world, 750 in around fifty genera in North America. Many have interesting sex lives. Some species are believed to be completely asexual with completely female populations. Others have strange reproductive cycles. Some bivoltine species (two generations per year) have generations which alternate between sexual and asexual (parthenogenetic), such that the sexual generation which has both male and female members will yield only females. The asexual (entirely female) generation will not mate, yet will yield both male and female offspring. Quite alien when compared to our human lives!

Tribe Cynipini

Andricus quercuscalifornicus gall
By far the largest and most conspicuous galls in the West, the large oak apple galls formed by the wasp Andricus quercuscalifornicus are familiar to many who live among oaks. Female wasps lay eggs on stems/twigs of various oak species. After the eggs hatch, the gall develops around the tiny larvae. Galls become very large, and occasionally multiple eggs are laid so the gall may support many larvae. Only parthenogenetic (asexual) females are known from this species.
Andricus quercuscalifornicus gall interior
Many other insects utilize the large galls or parasitize the larvae of the common Andricus quercuscalifornicus wasps. Inquilines include the moth Cydia latiferreana (Tortricidae) whose larvae feed on the inside of the gall. The moth larvae is then used as a host to the parasitoid wasp Bassus nucicola (Braconidae). Beetles (Ozognathus cornutus, Anobiidae) and termites (Rhinotermitidae) have also been found feeding on the gall material. Chalcid wasps in the families Eulophidae, Eurytomidae, and Torymidae have been documented as parasitoids of A. quercuscalifornicus, though surely there are many more inquilines and parasitoids than we know of.
Cynips mirabilis gall on Quercus garryana leaf (October)
A smaller yet more ornate gall is that of the gall wasp Cynips mirabilis. I found several small galls, perhaps twelve to thirteen millimeters in diameter, on the undersides of the leaves of Quercus garryana. It is probably safe to infer that eggs are laid sometime in the spring as leaves emerge, and development must occur within the year before the leaves drop in the fall.
Cynips mirabilis gall opened
Within the outer shell, a small hardened mass (which houses and feeds the larva) is suspended by delicate filaments. This gall is occasionally host to inquilines, since the larvae of moths (as yet unidentified) have been found within these galls.

Tribe Diplolepidini

Diplolepis rosae galls on a wild rose plant
As the specific epithet implies, Diplolepis rosae forms galls on a select few species of roses. D. rosae is a European native, accidentally introduced into the United States. Wasps lay eggs on the young leaf buds in spring as new leaves emerge. Multiple larvae feed on a single gall (personal observation), and they remain inside the gall throughout the winter before pupating and emerging as adults in spring. They are possibly parthenogenetic in some populations, as very few males have ever been documented. Ichneumonidae and Chalcidoidea wasps have been known to parasitize the larvae of D. rosae.

Superfamily Diaprioidea

The Diaprioidea is composed of the endoparasitoids of various Diptera, and occasionally Coleoptera or other Hymenoptera. They are small, obscure wasps, and only the most basic is known about their biology (something they have in common with many wasps in the Parasitica).

Family Diapriidae

At least three hundred species are found north of Mexico, with four thousand species estimated worldwide. They are parasitoids of fungus gnats and other dipterans, and often found in wooded areas with decaying vegetation (where their hosts are common).

Subfamily Diapriinae

Aneurhynchus sp. ♂
Aneurhynchus spp. are known to parasitize flies which feed on decaying plant matter, such as Fannia spp. (Fanniidae), Platypeza spp. (Platypezidae) and flies in the Sciaridae. These flies feed on either decaying plant material or fungus, mostly in wooded areas.
Aneurhynchus sp. ♂
I encountered this tiny wasp (~3mm) at my porch light at night. I imagine these are very common, yet are very often disregarded as small flies.

Superfamily Evanioidea

The Evanioidea contains three families: The Aulacidae, Evaniidae, and Gasteruptiidae. The Aulacidae and Gasteruptiidae are described below, but I have not encountered the Evaniidae, sometimes known as ensign wasps. Ensign or hatchet wasps (Evaniidae) are single egg predators within the egg cases, or oothecae, of cockroaches. Evaniids are peculiar in appearance for their much reduced abdomens, in contrast to the characteristic abdomens of the other two related families. There are at least 1,100 known species, probably many more, worldwide.

Family Aulacidae

The Aulacidae are a group of parasitoids often mistaken for ichneumon wasps which often share similar habitats and host preferences. Aulacids are often found in wooded areas. Aulacid wasps seek out wood boring larvae of beetles (several families, but mostly longhorns, Cerambycidae) and wood wasps (Xiphydriidae, Symphyta). Female Aulacids antennate the wood, seeking the host, and once a host is detected (perhaps they can sense the subtle movements of wood boring larvae?), they insert their ovipositor through the bark and into the host, where an egg is deposited.
Pristaulacus sp. ♂ (August)
I discovered a male Aulacidae, evident by the lack of the long ovipositor, struggling in a pool of shallow water. I attempted to rescue him in my hand where he proceeded to groom himself for about ten minutes before unexpectedly perishing.
Pristaulacus sp. ♂ (August)
One unique feature of this group of wasps is the high attachment point of the abdomen, something shared with the Gasteruptiidae which the Aulacidae is closely related. Also of personal fascination are the ridged on the top of the thorax. Aulacids are known to occasionally visit flowers for nectar, though I have not observed this directly.

Family Gasteruptiidae

The family Gasteruptiidae have unique and easily identifiable abdomens, though little is known by the lay observer of their biology. They are sometimes known as carrot wasps, probably a hint of the forage preferences of adult wasps seeking nectar, though they will visit other plants with small flowers that have easily accessible floral resources.
Gasteruption sp. ♂ on Allium cepa (June)
Larvae of gasteruptiid wasps are predators or predator-inquilines of other Hymenoptera that nest in pithy stems or twigs of woody plants. Predator-inquilines eat the larval food in the nest rather than the larvae itself, while predatory gasteruptiids feed on the larvae itself, such is the case for Gasteruption spp. Either way, the host larvae dies. Gasteruptiids go through winter as prepupae, then pupate in the spring.

Superfamily Ichneumonoidea

Over 6,000 species described north of Mexico, and at over 100,000 worldwide make up the superfamily Ichneumonoidea. The family has two major families: the Braconidae and Ichneumonidae. Both utilize a diversity of hosts across many insect orders and even some arachnids in various life stages from egg to adult.

The most peculiar feature among some of the Ichneumonoidea (notably the subfamilies Campopleginae and Banchinae in the Ichneumonidae, and subfamilies Microgastrinae, Miracinae, Cheloninae, Adeliinae, Cardiochilinae, Khoikhoiinae, and Mendesellinae in the Braconidae) is the presence of polydnaviruses in their genomes. Polydnaviruses are released into the host when an ichneumonoid is ovipositing, serving to suppress the immune system of the host and thus protecting the egg. The polydnavirus then infects the developing wasp larvae. Specific polydnaviruses have coevolved with the wasps they infect, and the wasps have evolved to be dependant on the virus to protect the developing wasp larvae.

Family Braconidae

Braconids and Ichneumonids are usually differentiated by their wing venation, but some other factors come into consideration. Braconids utilize a wide variety of hosts, including aphids, bark beetles, and caterpillars. Many species parasitize eggs of their hosts, but don't fully develop until the host reaches the larval stage. Unlike the Ichneumonidae, most braconids pupate in silk-like cocoons outside the bodies of their hosts either directly attached to the host or removed from it completely. Also unlike the ichneumonids, few braconids use hosts in the pupal stage to reach maturity, with the exception of the subfamilies Alysiinae and Opiinae.

Subfamily Alysiinae

About 2,300 described species make up the subfamily Alysiinae. They are small wasps, generally less than five millimeters but usually half that. While adults may feed on nectar and possibly pollen, they use various families of flies as hosts for their immature stages, mostly flies in the Agromyzidae, Anthomyiidae, Calliphoridae, Chloropidae, Ephydridae, Phoridae, and others. Female alysiine wasps lay their eggs in the eggs or larvae (maggots) of host flies, but don't complete their development until the host enters the next phase of development (either as larvae or pupae, respectively). In the case of larval-pupal parasitoids (those that parasitize the fly in the larval stage), they use specially adapted inverted mandibles to cut a hole through the hardened fly puparium instead of the mature fly. 
Alysiinae (October)
This wasp, probably less than three millimeters in length, was attracted to my porch light in the evening. Many small dipterans were also attracted to the lights, some may even been hosts for this small wasp but I never attempted to identify them. 

Subfamily Aphidiinae

Aphidiine wasps are not as numerous of the aforementioned wasps, yet are probably common where they are found. Around 120 species in sixteen genera inhabit the United States, and only 400 species in fifty genera are described around the world. They are endoparasitoids of aphids, which are only partially paralyzed before an egg is deposited. The host continues to develop while the tiny wasp larvae eats it from the inside, but dies as the wasp approaches the pupal stage. Aphidiines pupate within the empty shell of the host aphid after eating everything inside.
Aphidiine wasp (right) with a crane fly (Tipulidae, left)
Aphidiines are small wasps, not much larger than three millimeters in total length. The photograph I took is misleading, the crane fly in the background is much larger than the tiny wasp. Like some of the other small parasitoid wasps I've encountered, it was drawn to the light of my porch light.

Family Ichneumonidae

The Ichneumonidae, or ichneumon wasps, are endo- or ectoparasitoids of a wide variety of insects and arachnids (including immature or adult spiders, and egg sacs of spiders and pseudoscorpions). Their hosts are always insects which exhibit complete metamorphosis (where an insect goes through four distinct stages: egg, larvae, pupae, and adult) rather than incomplete or gradual metamorphosis. They often but not always have elongated ovipositors, and are partially distinguished from the braconids by a vein structure on their forewings which resembles a horse head, as well as a number of other anatomical structures. Like most Parasitica, they are incredibly difficult to identify and any attempt at identification should really be left to an expert.

Subfamily Banchinae

The Banchinae is a fairly common group of parasitoids with 1,500 species worldwide, and 600 north of Mexico. They are diurnal endoparasitoids of various larval Lepidoptera, Coleoptera, and Hymenoptera. Along with the Campopleginae, each species harbors its own genetically unique polydnavirus.

Tribe Atrophini

The tribe Atrophini uses lepidopteran (occasionally coleopteran) hosts, usually moths in the family Tortricidae, though they also parasitize moths in the families Pyralidae, Cossidae, Sesiidae, Gelechiidae, and others in both concealed and exposed locations. For these reasons, the genera Australoglypta spp., Cephaloglypta spp., Glypta spp. and possibly others have been used in biological control efforts. 
Cryptopimpla amblipennis (October)
Cryptopimpla amblipennis parasitizes larvae or prepupae of both beetles and moths (families Erebidae, Lasiocampidae, and Saturniidae) with short ovipositors. Development of the wasp is completed when the host enters the pupal stage and has built a cocoon.
Cryptopimpla amblipennis (October)
Like a few the other wasps here, this wasp was drawn to the light of my porch light. It flew around then landed on the glass of the lamp and walked around. This was repeated for an hour, at least.
Lissonota sp. ♀ (October)
Lissonota spp. are endoparasitoids of Lepidoptera in concealed locations, probably in wood. The host is only partially paralyzed during oviposition, then continues to develop. The wasp matures after the moth has built its cocoon.
Lissonota sp. ♀ (October)
I discovered this small wasp (around one centimeter long) on the side of a beehive on a cool day. Perhaps it was attracted to the warmth of the hive?

Subfamily Ophioninae

Despite only having thirty-seven species in nine genera in the US, the Ophioninae are some of the most common ichneumon wasps encountered. Many are nocturnal, and drawn to lights, while others are diurnal or crepuscular. Most are endoparasitoids of lepidopteran larvae, though at least a few parasitize beetle larvae. Most prey on host caterpillars that feed on vegetation such as members of the families Noctuidae, Lasiocampidae, Lymantriidae, Saturniidae, Geometridae, Arctiidae, and Sphingidae. The ovipositor is very sharp (although they've been known to sting humans) and paralysis of the host is temporary.
Ophion sp. (March)
Ophion is a very common genus in both the United States and in the United Kingdom, where they are often drawn to lights at night. Most species are nocturnal, when they seek caterpillar hosts. Usually one egg is laid in each host. Development of the host continues until it reaches the pupal stage when it typically dies while the wasp remains inside to pupate itself.

Subfamily Ichneumoninae

The subfamily Ichneumoninae is made up of both ecto- and endoparasitic wasps which parasitize caterpillars of both lepidopterans and symphytans (sawflies). They have short ovipositors, so must find hosts that are in exposed locations such as external plant feeding caterpillars. Ichneumonine wasps are idiobionts, meaning their hosts cease or slow development after oviposition. Hosts are parasitized typically in the larval or pupal stage, but wasps always emerge from pupae. Adults occasionally eat large portions of the host bodies, sometimes killing them in the process. Adults also feed on honeydew from aphids or other sap sucking insects, and are said to eat the foliage of certain plants themselves.

Tribe Ichneumonini

The tribe Ichneumonini are represented by over 450 species north of Mexico, one third of which are in the genus Ichneumon.
Spilichneumon sp. (March)
Spilichneumon spp. are internal parasitoids of noctunid moth larvae. The caterpillar reaches the pupal stage, then perishes as the wasp continues to pupate and later emerges from the chrysalis. Adult wasps overwinter as adults, then seek prey in leaf litter the following spring. I discovered this wasp on sticky whiteleaf manzanita (Arctostaphylos viscida) where it may have been feeding on honeydew or perhaps the sticky secretion of the plant itself.

Superfamily Formicoidea

Family Formicidae

The monotypic family Formicidae, the ants, are represented by 14,000 species worldwide. They evolved from wasps between 110 and 130 million years ago. Most are eusocial with fully defined castes, or are workerless parasites which require the eusocial medium of a host ant's colony to reproduce and survive.

Ants are differentiated from wasps by the constriction of their waists, which typically have two or three points of constriction rather than the single point of constriction of most wasps. Ants have elbowed antennae, while very few wasps have elbowed antennae, but the wasps that do have elbowed antennae live solitary lives while all ants are social. Ants are typically wingless, except during mating cycles when winged male and female (queen) ants leave the nest to mate with ants from different colonies and form new colonies. Males die after mating, and females lose their wings after they have finished mating. Females may life from one to over twenty years, depending on the species.

Ant diets vary widely. Some feed on fungus they tend to in the nest, others feed on honeydew, plant nectaries (floral or extrafloral), or other insects. Few are considered to be pollinators, although there are some orchids specifically pollinated by ants (i.e. Chamorchis spp., Microtis spp.). The chemicals secreted by ants are damaging to the pollen of some plants, and although ants may be seen visiting a wide variety of flowers for nectar, the pollen that adheres to their bodies may be rendered sterile. Admittedly, it is an understudied topic and there are probably more ant pollinated plants than we are currently aware of.

Subfamily Formicinae

Named for the ant genus Formica (Latin for ant), the Formicinae are occasionally large wasp-like ants complete with a vestigial stinger and venom gland for production and retention of formic acid. Most feed on nectar and honeydew, but some species are also scavengers or predators.

Tribe Camponotini

Camponotus sp. (June)
The carpenter ants (Camponotus spp.) are large and conspicuous ants associated with rotting wood. Despite their name, they don't eat or chew sound wood but rather infest wood that is already compromised from dry rot (fungal) or other causes of decay. Nests can be in wood (fallen logs, or in this case, house siding) or in the ground, rarely in living wood. They are generalists and omnivorous, eating a wide variety of foods including honeydew, sap, living or dead insects, or a variety of other things. In the evenings they are often found to be grouped near the entrance of their nest, and will all eventually move inside.

Subfamily Myrmicinae

The Myrmicinae are highly variable in size, with the smallest being about one millimeter and the largest up to one centimeter. Many species are generalist predators, although many others are seed harvesters. Others still are fungal cultivators, collecting plant material to grow their subterranean fungus crop.

Tribe Attini

Pheidole sp. (August)
Big headed ants, Pheidole spp., are so named for the large heads of some of the workers (the majors, the minors are smaller). Many species of ants exhibit polymorphism, where two or more forms of a single caste have different proportions and with them slightly different tasks. Many species of Pheidole are generalist scavengers which feed on a wide range of prey items, while others are seed harvesters. They were mostly active at dusk when the temperatures began to drop. Harvester ants typically forage in hot dry periods, but they obtain water from metabolizing the fats within the seeds (or other prey items) they gather.
Pheidole sp. (August)
The orange mass is a piece of protein supplement made for honeybees. I was curious if they would have an interest in it as food. The pollen patty was of minimal interest to the ants, who were probably more interested in seeds than the soy and sugars that made up the supplement.

Tribe Stenammini

Aphaenogaster sp. (August)
Aphaenogaster contains seed harvesting, scavenging, and aphid farming species. These are agile, and somewhat large ants (though not as large as Camponotus) with long legs and slender bodies. This helps them steal prey from other predators, being the opportunists that they are. On occasion some species tend to aphids feeding on roots of plants within their nests, the ants themselves feed on the honeydew excreted from the aphids.

Most species of Aphaenogaster nest in the ground among stones or logs, and their nest entrances can sometimes be identified by a ring of pebbles and other debris. They are active at dusk when it is very warm, since they are active primarily in summer in my area. Nests move frequently, perhaps to find new host roots for their aphid associates. I attempted offering them a piece of pollen substitute (made for honeybees) and unlike the Pheidole ants they were apparently quite pleased with it as much of it was eaten.
Aphaenogaster sp. (August)

Last year I documented nine species of wasps from six families. This year I documented at least twenty nine species (including the ants) in at least twelve families. The more I learn about the amazing variety of wasps in the world, or even just around me, the more enthralled I become. Wasps are the progenitors of modern bees and ants, and their contribution to our world and our lives is untold. I am optimistic that by showing my photos and compiling what I have learned and observed about the wasps within my periphery I can show others that wasps are not to be feared or eliminated but celebrated and cherished. Wasps are pollinators, predators, and food for vertebrates (including humans, in some cases). Learn about wasps, make some observations of your own, and report your findings. What could possibly go wrong?


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Mischocyttarus flavitarsis ♂


  1. Whew. So, do we have pollen wasps in OR? (Pollen wasps, subfamily Masarinae)
    Your info about them did not clearly state that, and you had no picture. According to wikipedia (sorry) "They are most diverse and abundant in the desert regions of southern Africa, but also occur in the deserts of North and South America. Some species of Pseudomasaris in California, such as Pseudomasaris vespoides, bear a remarkable resemblance to yellow jackets, ....."

    1. You are correct, we have neither pollen wasps or honey wasps in Oregon


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