Monday, May 14, 2018

Bees in Spring 2018

Spring is the best time in Southern Oregon to watch bees! The combination of highly diverse wildflower communities, excellent climatic conditions, and a relative abundance of water culminates to produce a great situation for many species of bees. Without looking up the data, I would bet that the highest diversity of bees can be found in the spring months in Southern Oregon. Not only have I seen more different kinds of bees in the spring than in summer or fall, but there are more native plants in bloom in Southern Oregon than later in the year which offer a diverse nutritional palate.
A honey bee clings to a willow catkin with one leg while grooming the pollen into her pollen baskets. February 22nd.
The earliest blooms in Southern Oregon are found on the trees. Alder, hazel, and willow are some of the first trees to bloom and produce an abundance of pollen for the few bees active at this time as well as a plethora of flies and beetles that feed on pollen. When apiaries or the odd feral honey bee colony are located near any of these trees, often near bodies of water, they delight in the abundant pollen on warm sunny days. Few native bees are active in January or February when the earliest blossoms appear, but I saw Andrena and a few bumble bee queens foraging on willow catkins in February this year.
A mating pair of Ceratina on pear blossoms. April.
Southern Oregon in April is host to billions of pear blossoms. Pear orchards are fairly commonplace around Medford, though many have been sold and turned into housing developments or hemp farms, much to the dismay of bees and other pollinators. Pear growers use honey bees to pollinate their trees, but the beekeepers make a fraction of what they are paid per hive in the almond orchards in California. Where almond growers may pay up to $200 per honey bee hive in the almond orchards of the Central Valley in California, pear growers rent less hives and might pay up to $40 per hive. This is probably because almonds bloom much earlier than pears, a time when few native pollinators are active, and almonds are currently much more valuable than pears. Consider the cost of pears compared to the cost of almonds next time you go grocery shopping.
A mating pair of Ceratina on pear blossoms
The pear orchards of Southern Oregon, at least the ones I have been in, are surrounded by a lot of natural landscapes and filled with flowering weeds. Whereas almonds are harvested by shaking the trees and then raked from the ground, the floor of the almond orchards needs to be bare or mowed. Pears are not collected this way, so the ground beneath the trees is sometimes overgrown with weeds. This offers a lot of resources for native and managed bees alike.
Osmia on a crab apple blossom. May.
Apple blossoms follow the pears. I am not sure there are many apple orchards in Southern Oregon, but they are grown as ornamental trees and personal orchards. Mason bees, Osmia spp., are sometimes managed for pollination of spring tree crops including almonds. Unlike honey bees, each female creates her own nest and does not live socially. In fact, most female native bees fulfill the role of both queen and worker. Osmia are called mason bees because they use mud to build the cell walls and partition cells in their nests (preexisting linear tunnels, usually in wood).
Nomada on a crab apple blossom
Peculiar, wasp-like, and fascinating. That is how I like to introduce the cuckoo bees. As the common name implies, they steal the nests of other bees. Unlike the birds of the similar name, cuckoo bees lay an egg in the cell of a host bee, such as Andrena or Halictus, and the cuckoo bee larvae usually kills the host larvae and develops on the food (a ball of pollen) collected by the host bee. Since the cuckoo bees steal nests from other bees, they don't create nests themselves. Since the nest they steal is provisioned by the host, they have no need to collect pollen, and thus they don't have pollen collecting hairs on their bodies.
Nomada female searching for host bee burrows
Cuckoo bees in the genus Nomada are usually black, yellow, red, or a combination of those colors. I was lucky to see a few red and black females hovering just inches from the ground recently. They were seeking host nests, probably Andrena or Halictus which nest in soil. Nomada females find Andrena nests by olfactory cues (Cane 1983).
Anthophora female on Phacelia tanacetifolia. May.
Phacelia tanacetifolia, or lacy phacelia, is a member of the Boraginaceae, native to California and possibly Oregon. It is more commonly available as seed and usually grown as a cover crop, ornamental, or sometimes specifically for bee forage. It doesn't let down, it is a great bee plant. Bees of all shapes and sizes, as well as a variety of other types of pollinators, are attracted to the blue scorpioid inflorescences.
Anthophora female on Phacelia tanacetifolia
I recently had the opportunity to observe bees visiting a large planting of P. tanacetifolia at Easy Valley Farm in Rogue River, OR. One of the more conspicuous types of bees were the large and fast digger bees. Anthophora is a common and widespread genus with some species remaining active from spring to fall. While some solitary bees only have a single generation each year, some species have two or multiple generations. At least some if not most species of Anthophora produce offspring all year, with the last generation of the year overwintering as prepupae within underground nests.
Halictus on Phacelia tanacetifolia
Sweat bees, more accurately known as halictid bees since not all species are attracted to sweat, are very active in spring and summer. They vary widely in size and nesting habits, and are very widespread and speciose.
Bombus vosnesenskii clinging to an Anchusa azurea blossom
An Old World member of the Boraginaceae, Anchusa azurea is found in my garden and in those fortunate enough to have acquired it from seed. It is like a large forget-me-not, and is very attractive to bumble bees and honey bees. I photographed an odd flower with only four lobes, most have five, with a bumble bee clinging to it early one morning. This bumble either was caught in the cold and unable to return home, or wanted an early start.
Iris chrysophylla with a bumble bee
Iris chrysophylla, yellowleaf iris, is a dryland iris found among grasses in mixed coniferous forest clearings and edges. It blooms profusely in mid spring over a long period in Southern Oregon. Various bees visit the flowers, including mason bees, halictid bees, and bumble bees. Though it is visited by various bees, I do not typically see a lot of bees visiting the flowers even where it is blooming in large masses.
Bombus diving for nectar on Iris chrysophylla
Iris flowers, as well as a few other Iridaceae relatives found around the world (i.e. Hermodactylus, Moraea), are complex and peculiar. To oversimplify, each single flower is divided into three ports of access for bees to enter seeking nectar. Pollen is typically deposited onto the back of the bee, but only if it enters the correct way. Bumble bees have very long tongues and are able to circumvent the reproductive structures and access the nectar from the side.
A honey bee forages for nectar on Calochortus tolmiei
While Iris chrysophylla grows from a short rhizome, Calochortus tolmiei grows from a bulb. Calochortus is only found in the New World and is very unlike other New World bulbs in flower structure. C. tolmiei is one of a handful of species with peculiar hairs on the petals, likely an adaptation to prevent inefficient pollinators from stealing the nectar. Nectar is excreted from colored patches at the base of the petals, and the hairs force the bee to rub against the anthers to access it.
Calochortus tolmiei and a honey bee fleeing from a camera that came too close for comfort.

Saturday, March 24, 2018

Arctostaphylos viscida

From left: Callophyrs augustinus and an empidid fly nectaring on Arctostaphylos viscida.
Arctostaphylos viscida Parry (Sticky whiteleaf manzanita) is in full bloom here in Southerstern Oregon. Manzanitas are in the family Ericaceae, which includes related genera Arbutus (madrone, strawberry tree), Calluna (heather), Erica (heath), Kalmiopsis, Pieris, Rhododendron (includes azaleas), Vaccinium (blueberries, cranberries, etc.), and over a hundred more genera, few of which known in cultivation. A. viscida is native from Southwestern Oregon south through most of California (to Kern County, possibly further south). It is a shrub or small tree, sometimes reaching a height of fifteen feet in optimal conditions, shorter further south. Small panicle-like clusters of urn-shaped flowers appear in Spring. The entire inflorescence is sticky, covered in glandular hairs, with glaucus leaves, thus the common name.
Arctostaphylos viscida, a variant with white florets
Sticky whiteleaf manzanita grows in association with oak (Quercus), Pacific madrone (Arbutus menziesii), various conifers (JuniperusPinusPseudotsuga), and Ceanothus among others. With many of these, it shares a variety of endo- and ectomycorrhizae, which are types of fungi which survive on or within the roots of a host and trade valuable nutrients (as well as increasing the surface area of the roots) for carbon and other exudates (root secretions). Dozens of species of mycorrhiza have been discovered in association with Arctostaphylos and associated plant species. Essentially, mycorrhizal fungi are symbiants which infect their hosts, but they benefit the plants in multiple ways and are necessary for the establishment and survival of countless taxa in the plant kingdom. Like all ericaceous plants, Arctostaphylos requires symbiosis with specialized ericoid mycorrhizal fungi to survive in the acidic and nutrient poor soils they are typically found in.
Arctostaphylos viscida flanks the northeastern rim of Upper Table Rock in Central Point, OR
Arctostaphylos viscida is a pioneer shrub, entering the landscape in succession following grasses and other herbaceous plants. A. viscida paves the way for trees such as Douglas-fir (Pseudotsuga menziesii), and contributes to its establishment by hosting the necessary mycorrhizal fungi that Douglas-fir requires to survive. The same group of mycorrhiza also aids in the establishment of Arbutus menziesii, a relationship which may explain why madrone is so difficult to keep alive in cultivation (lacking the correct mycorrhizal symbiosis outside its native range).
Flowers of Arctostaphylos viscida with banded thrips, Aeolothrips sp.
The flowers of Arctostaphylos viscida are similar to many (but not all) ericaceous plants such as ArbutusPieris, and Vaccinium by having fused petals forming an urn or cup, a stigma nearly twice the length of the stamen, and a ring of stamen surrounding the ovary and nectaries. Manzanita pollen is dehisced through small pores and often requires sonication, or buzz pollination, to release the pollen. Small insects such as thrips, which are small enough to crawl into the flowers, can gather pollen without the use of sonication. A. viscida may occasionally be self-compatible but progeny probably benefits most from cross pollination between different plants. Bloom time varies between individual specimens, as does the relative attractiveness to pollinators due to unknown factors that may include the health of the plant, quality of the nectar, or something else entirely.
Arctostaphylos viscida bark
The bark is similar to that of madrone (Arbutus menziesii): cinnamony, thin, and smooth once the outer layer of bark peels off. It has the unique characteristic of repelling water. This feature may contribute to the plants ability to survive in severe drought, though if there is inadequate rain or sun they do not flower well. Arctostaphylos viscida shrubs that grow on the north side of structures or under dense canopies of trees do not seem to flower reliably. The excessive shade from a northern exposure or tall trees promotes fungal infections that result in aborted buds and black spots on the leaves. A. viscida prefers open sunny habitats, and is more fit in chaparral than in dense woodlands, though it does perfectly well at forest edges, clearings, and slopes which in some aspects have similar characteristics to true chaparral.
From left: A. viscida berries, crushed dried berries, and seeds.
Seeds of Arctostaphylos are produced in the form of berries. In A. viscida the berries are sometimes sticky, but this seems to go away when the fruit is mature. There is speculation that the berries (and seeds) are distributed by animals, probably birds. Laboratory tests of seed procured from coyote feces (what a fun job that must have been) found low germ rates. Birds are more likely, as the berries would likely pass through quickly (acid treatment in a lab helped break seed dormancy). Fire is another treatment that helps scarify the seed and break dormancy, and has the added benefit of reducing competition (especially tree saplings) which would otherwise shade out the slow growing manzanita. Suppressing fire is probably hindering the development of new colonies of manzanita. By briefly examining many of the stands in my area, it is difficult to find small young plants, but mature plants 6' or taller are common.
A honey bee, Apis mellifera, seeking nectar
Many insects, including the introduced European honey bee (Apis mellifera), visit manzanita flowers where they are abundant. An individual plant can produce hundreds of thousands of individual florets that open over the span of a few weeks. Bees and flies are the most common visitors to the flowers, though the abundance of either depends largely on the surrounding habitat. For example, plants growing among conifer forests may have more flies than bees, since conifer forests tend to support less bees than do chaparral or oak woodlands. Honey bees will work the flowers when both are abundant, though in dry years they may not be able to reach the nectar since most plants produce less nectar in drought. Other insects occasionally bite holes in the sides of the flowers to reach the nectar, and when that happens honey bees will gain access to the nectar through the side as well though it is unlikely they will create the holes themselves.
A bumblebee queen, Bombus vosnesenskii, collecting nectar.
The primary pollinators of manzanitas are typically medium and large bees which are capable of sonication, or buzz pollination. The bee lands on the flower and vibrates the flight muscles which releases a burst of pollen from the pores in the anthers. A positive electric charge (which all flighted insects generate) helps the pollen cling to the bee. Bumble bees (Bombus), mason bees (Osmia), digger bees (Anthophorini), and long-horned bees (Eucerini) are capable of sonication and I have observed all visiting A. viscida in my observations.
Male Andrena sp., robbing nectar through a hole in the side of the flower.
Many smaller bees visit the flowers, and in my observations many of them are nectar thieves. It's unclear who is chewing the holes in the flowers, but once they are there the flower has a low chance of getting pollinated since most of the visitors to those flowers bypass the reproductive structures and feed on nectar through the hole.
A cuckoo bee, Nomada sp., robbing nectar from a hole in the floret.
I have personally observed many types of small bees visiting A. viscida including mining bees (Andrena), small carpenter bees (Ceratina), and cuckoo bees (Nomada). Cuckoo bees are kleptoparasitoids, like cuckoo birds, who lay their eggs in the nests of other bees. Cuckoo bees forgo the creation of their own nests, and do not collect pollen. Instead, cuckoos rely on the provisions supplied by host species, usually other closely related bees. The invader sneaks into the nest while the host is out and lays an egg in a cell chamber. When the cuckoo bee larvae hatches, it kills the host larvae then feeds on the host provisions and develops in the host nest until adulthood. The genus Nomada, sometimes called nomad bees, are in the Apidae, the family that includes honey bees, bumble bees, digger bees, carpenter bees, and a few more. Mining bees, Andrena, are typical hosts for nomads, but others include Agepostemon (green metallic sweat bees) and a few others.
From left: a mason bee, Osmia sp., perched on a leaf, and a paper wasp.
Many types of bees mate on and around wildflower patches, and this includes manzanitas in full bloom. I have captured and observed male mason bees (Osmia), male long-horned bees (Eucerini), male mining bees (Andrena), and male carpenter bees (Ceratina) in close proximity to A. viscida. Many mate while foraging, unlike honey bees. While honey bee queens mate with several males and don't forage, the majority of native bees mate with a single male while foraging. Male honey bees, or drones, mate with a single queen and then die, while the majority of native bee males mate as much as possible with as many females as they can mount.
 Mischocyttarus flavitarsis
Vespid wasps are typically just getting started while A. viscida is in bloom in Southern Oregon. Females which hibernated through winter are just beginning to emerge pending good weather, and they are keen on acquiring the much needed carbohydrates supplied by flowers in the form of sugary nectar. The beginning of the year for yellowjackets and paper wasps is not dissimilar, as mated females must create their nests and feed the first of their offspring before matured workers are able to take over the foraging responsibilities so the queen can stay home and devote the remainder of her life to laying eggs. Yellowjackets, genus Vespula, are similar to honey bees in that there are distinct castes (reproductive queens, males, and workers). If yellowjacket workers do lay eggs, they will only rear male offspring since the workers are not equipped to mate. Paper wasps (Polistes and Mischocyttarus) have females that are all capable of mating and thus laying both male and female offspring. While there are no true paper wasp queens, a dominant laying female asserts her sovereignty by fighting with competing females (size is often a factor of success).
A parasitoid wasp, Ichneumonini
Many parasitoid wasps congregate on and around A. viscida for nectar and honeydew, as well as to seek out hosts. I've observed ichneumonoids and chalcidoids either seeking hosts or seeking sustenance. Many suitable hosts are found on A. viscida, including many lepidopteran caterpillars.
Male ant, Lasius sp., stuck to the sticky inflorescence.
The sticky inflorescences of A. viscida trap many small insects, notably small flies and winged ants. Winged ants were one of the unfortunate insects to get stuck to the inflorescence. Ants in the genus Lasius are often attracted to honeydew, the frass of sap sucking insects like scale or aphids. Subterranean species of Lasius feed on the honeydew of root feeding aphids, forming mutualistic relationships.
A bee fly, Bombylius major, feeding on nectar
Flies visit A. viscida flowers frequently, and may also be gathering around the plants to mate or seek out prey (predatory species). More diverse and speciose than bees, flies are reliable pollinators in climatic conditions not accommodating to most bees. Many flies mimic bees and wasps, although flies are incapable of stinging. Bee flies, Bombyliidae, not only do a good job at mimicking bees, some are even parasitoids of ground nesting bees.
Dagger flies, or dance flies, are named for the long rigid proboscises they possess and the distinctive courting rituals performed by the males. Not all species have a long proboscis, but those that do use them to probe flowers for nectar. I have seen them visiting many early blooming trees such as Prunus and Salix, and early blooming ephemerals like Crocus and Muscari. They are also predatory, feeding on smaller flies, while larvae feed on decaying matter in the soil.
Empididae infected with Entomophthora fungi
I've seen several dead flies clinging to leaves and flowers, having been infected with the fungi Entomophthora. Spores are forcibly ejected from specialized structured grown by the fungus from membranous sections of the abdomen. Flies under or downwind may inadvertently catch a spore which proceeds to grow into the unsuspecting fly. The fungal hyphae gradually grow throughout the entire body, digesting the flies organs, and when it reaches the brain causes the fly to land and climb upwards. When the fly dies, after about a week from becoming infected, spores are produced and the cycle is renewed. Entomophthora isn't restricted to flies, some species infect aphids, mites, grasshoppers, and others.
Noctuidae caterpillar
A handful of moths in the Noctuidae and Geometridae use A. viscida as a host plant. Caterpillars are often difficult to see unless one is seeking them out, due to their drab colors and patterns. Adult moths of various types visit the flowers for nectar.
Nymphalis californica
During warm weather, butterflies visit the flowers. I have found this to be true only in clearings with a lot of direct sunlight. Manzanitas that receive only filtered light appear to be less attractive to butterflies. Adult butterflies were seen sunbathing as well as nectaring, while on a few occasions males attempted to defend their territory from other species. I suspect courtship may also occur in the vicinity as well, though I didn't observe it directly. California tortoiseshells, Nymphalis californica, overwinter as adults and benefit from access to early nectar sources such as A. viscida.
A mayfly, Ephemeroptera
Mayflies live for about a day as adults, and are incapable of eating. Thus, a mayflies presence on A. viscida flowers was purely coincidental. Mayflies spend one to several years as aquatic nymphs before reaching adulthood, feeding on algae and detritus from under rocks at the bottom of streams, rivers, and occasionally lakes.
Banded thrips, Aeolothrips sp.
Thrips, at least in some areas, are very numerous on and within the flowers of A. viscida. Thrips feed primarily on plant tissue, including flowers, buds, and pollen. But despite their reputation, they may also be pollinators. Thrips have been demonstrated to be pollinators of many plants in many regions of the world, from tropical environments to high altitude and high latitude alpine and tundra landscapes, respectively. They may also be some of the most ancient pollinators. Whether or not they benefit A. viscida through direct pollination or not, they may serve the plant by attracting hummingbirds which feed on them as well as feeding on nectar, facilitating pollination. Rufous and Anna's hummingbirds, Selasphorus rufus and Calypte anna, respectively, are suspected to feed on both thrips and nectar during their visits. Conversely, high numbers of thrips on a particular inflorescence appear to keep other pollinators (i.e. bees) from visiting that inflorescence in my observations, although the thrips occupation varies from inflorescence to inflorescence on a single plant.


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Monday, February 12, 2018

Parasitoid Wasps of Southern Oregon 2017

Anyone that knows me knows that I love wasps. I think you should love them, too. Here I will attempt to familiarize you with the world of the non-stinging wasps known as the parasitoids. Parasitic wasps do not have true stings, as the aculeate wasps [and bees] do. These parasitoids have ovipositors, which are used to lay, or sometimes inject, eggs. While there are aculeate parasitoids, the aculeates do not have ovipositors. (The exception is the Chrysididae, the cuckoo wasps, which are aculeates which evolved their own unique ovipositors independently from the parasitoids featured in this piece.) The aculeate sting evolved from an ovipositor many millions of years ago.
Female snakefly with ovipositor, Raphidioptera
Wasps are in the super diverse order Hymenoptera, which also includes bees, ants, and sawflies (including horntails). This huge, and old, lineage holds more species than there are known vertebrates in the world. The orders Hymenoptera, Coleoptera (beetles), and Raphidioptera (snakeflies), among a few other orders, are thought to have evolved from a common ancestor in the Permian period. The earliest hymenopterans, the sawflies, suborder Symphyta, first appear in the Triassic period. Most sawflies (and horntails) are phytophagous, meaning the larvae feed on plant material. The first true wasps appear in the mid-Jurassic period, and the earliest known bees in the Cretaceous along with flowering plants.
A colorful male Ichneumonidae metasoma
There are over 130,000 species of wasps and bees worldwide with new species being described each year. Parasitic wasps, more ancient and possibly more speciose than the aculeate wasps and bees, have very diverse features and characteristics not found among aculeates. These features represent the diverse behaviors and life styles of the thousands of parasitic wasps found throughout the world.
Ichneumonidae antennae with many flagellomeres
Sexual dimorphism is common among the Hymenoptera and there are many features that can be used to tell the sex of individuals. The antennae of aculeates have similar numbers of flagellomeres (antennal segments) between families and can be sexed based on the number (females have ten flagellomeres while males have eleven). Parasitoids occasionally, however, have many flagellomeres and the number differs significantly between species. Males don’t lay eggs, so individuals of species which have long ovipositors can be sexed based on the presence or absence of the ovipositor. Males, in general, are difficult to identify to species since many species resemble each other, while the females bear traits that offer the best means to identify a species.
Torymus female, Torymidae, reared from a mossy rose gall 
The ovipositor of parasitoids can be long or short, and in many cases is at least partially retractable. In the case of many the ovipositor is protected within a sheath which is usually visible at all times. Lay observers of the unenlightened kind often mistake the ovipositor sheath for a sting and demonstrate unnecessary uneasiness towards the poor creature. Long ovipositors are not adapted to penetrating human skin, nor do the wasps possess a venom that would inflict any pain worth calling mother about. Some species do have short, rigid ovipositors which could potentially poke through the skin if the wasp is handled. The best advice is to leave the wasp alone if at all possible. Even if it is not capable of stinging, your attempt to coerce it onto your face would probably stress it out, and nobody needs that.
Cryptini female
Parasitoid wasps possess venom, though unlike their eusocial aculeate cousins the venom is adapted specifically for host species. Similarly to many aculeate wasps, parasitoid venom is composed of a cocktail of proteins, peptides (including kinins, found in many wasp venoms), and many toxins (the chemistry, admittedly, is beyond my education level). Some of the wasps in the families Braconidae, Ichneumonidae, and Pteromalidae possess polydnaviruses (which evolved independently in all three cases) which serve to interfere with the hosts’ immune system. Venoms injected alongside the polydnaviruses, at least in the case of the bracoviruses (the polydnaviruses possessed by braconids), further aid the pathogen to do its job. In the case of eggs injected into the host, the venoms and polydnaviruses help ensure the survival of the wasp egg(s) and larvae.
Toryminae female; Torymidae, reared from a mossy rose gall
Parasitoid venoms exhibit other characteristics including antimicrobial and biopesticidal properties. The lethality or paralyzing effects are sometimes highly dependent on the age of the host, and in some cases highly species specific. Some venoms send the host into premature pupation which the wasp larvae may need to develop properly. Other venoms simply block neurotransmitters or neuromuscular transmission which may protect an egg being deposited to the exterior of a host. Another effect of the venom of at least some braconids is the alteration of the host hemolymph for the nutritional benefit of the wasp larvae, or in other cases causing the host to become lethargic resulting in easier oviposition or protection for the immature wasps.
Gasteruption and a small solitary bee
Many adult parasitoids visit flowers for nectar or occasionally for sugary sap or honeydew, and the presence of flowers may even extend the lives of adult wasps. Many parasitoid wasps have short tongues and so only benefit from small flowers with very exposed nectar. Flowers in the Apiaceae such as herbs including parsley or coriander as well as vegetables like celery or carrots are all great plants for parasitoid wasps and will also benefit small bees and a myriad of other small beneficial insects. The composite family, Asteraceae, also has many good species for wasps. When choosing species for parasitoid wasps, select species with many small flowers instead of few large flowers. Deep tubular flowers will not benefit short-tongued wasps, but will instead be more attractive to birds, butterflies, or large bees. Planting anything is better than nothing, and planting native plants is best. Parasitoid wasps may indirectly benefit from planting host plants for insect hosts (i.e. plants which attract aphids for aphidiine wasps).
I've been observing wasps in close detail for the last several years. They just fascinate me. When I was a kid I loved watching the silicon-based extraterrestrial parasitoids in the Alien movies designed by the late H.R. Giger, creatures which I still find both terrifying and beautiful. We are fortunate that parasitoid wasps, which aren't too different from the parasitoid aliens in some of their lifestyles, are comparatively small and do not use our bodies as hosts. Below are many of the parasitoids I had observed in 2017 through both direct organic observation and capture. Most of the encounters were completely by chance, but by realizing that these wasps are practically everywhere and knowing what to look for, you too will begin to discover tiny aliens in your backyard, workplace, and probably everywhere else you go.
Cryptinae female with a US cent coin


Some of the most recognized and speciose of the parasitoids are the wasps in the Ichneumonoidea, the superfamily which includes the ichneumons and braconids. There are over 6,000 species described north of Mexico, and at over 100,000 worldwide. Both ichneumons and braconids 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.


The Ichneumonidae, or ichneumon wasps, are ecto- or endoparasitoids (external and internal parasitoids, respectively) 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.
Fused cells in ichneumon forewings create the "horsehead" often used in determining Ichneumonidae from Braconidae. The small hairs, or setae, protect the membranes, help create lift, and demonstrate hydrophobic effects.


The subfamily Ichneumoninae is made up of both ecto- and endoparasitic wasps which parasitize caterpillars of both lepidopterans (mostly moths) 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.
A male ichneumon (Ichneumonini tribe) which I captured in a field of drying grasses. I captured (and released) many of these individuals in the same field. It is likely they were seeking females to mate with. Male ichneumons are often colorful while females tend to be drab.
Many of the ichneumons are cryptic and only known from host records, meaning a researcher collected infected insect larvae or pupae and watched what emerged from its dead or dying body. Courtship and mating among ichneumons is studied to some extent but few broad scale studies have been done, with most research focusing instead on one to few closely related species.
Captured male ichneumon (Ichneumonini tribe)
Solitary females of most hymenopterans, with the exception of honey bees, usually mate with a single male while males may mate with several females. This is partially true with ichneumons. Solitary ichneumons, that is species which lay a single egg in each host, typically mate with one or less often two males. Gregarious species, females which lay more than one egg within a host, mate with multiple males.
Ichneumonini tribe
Males of most species emerge prior to the emergence of the females, occasionally congregating near the pre-emergent females. Males of some species, such as giant ichneumons, Megarhyssa spp. (Rhyssinae), inseminate pre-emergent females by inserting their elongated abdomens into the exit burrows. Insemination of this type is usually successful, though post-emergent fertilization on the tree bark with freshly emerged females has also been observed although it is less successful.
Early spring in Corvalis, Oregon, I captured and released this ichneumon (Ichneumonini tribe) which was near the entrance of a honey bee hive. The weather was overcast, windy, and wet, and it is possible this wasp was attracted to the warmth of the colony or an associated lepidopteran host.
Male ichneumons seek females with the aid of pheromones produces by the female, or by honing into the scent of a particular host plant (such as a plant in/on which the wasps’ host insect is found). In some cases both virgin and mated females exude pheromones. When male ichneumons discover a mate, they probe the female with their antennae to orient themselves for fertilization. In the case of Pimpla turionellae (a European species), and perhaps many others, male pheromones excreted from specialized glands on the antennae aid in female receptiveness when the males probe the female antennae. This antennal probing is sometimes done throughout the duration of intercourse which can take from between 1 to 20 minutes depending on the species, though mating acts have rarely been directly observed.

Some ichneumon females are ready to oviposit almost immediately after mating. Adult longevity and host availability are inherently connected as statistically the longer an adult female lives the more likely she will find hosts to oviposit in. Floral hosts (i.e. dandelions) and sources of honeydew (sugary frass from sap-sucking insects such as aphids) have been demonstrated in a few economically important ichneumons to increase adult longevity thus increasing their effectiveness as biocontrol agents.


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.
Exetastes (Banchinae)
Exetastes is a fairly common genus found worldwide with the exception of Antarctica and Australia. They inhabit mostly unforested landscapes like chaparral and oak savannas, or sometimes in large forest clearings. Adults visit flowers frequently. I have observed Exetastes visiting Daucus (carrot) for nectar in early autumn. The individual photographed here was captured in low grasses midday on a sunny southern facing hillside.
Exetastes (Banchinae)
Exetastes (Banchinae)
Hosts for Exetastes are usually cutworms (Noctuidae). Host larvae live to initiate pupation (whether it is initiated prematurely or not is unknown) in the soil by forming a pupal case. The wasp larvae kills the host after the pupal case is constructed and pupates within it.


The Cryptinae is the largest family of the Ichneumonidae with over 400 genera worldwide. They are mostly ectoparasites of a range of hosts including lepidopterans, coleopterans, dipterans, and even other hymenopterans. Some are hyperparasitoids of other parasitoids in the Braconidae and other ichneumonids. Females of some species are wingless (i.e. some Gelis).
Some cryptines are at least partially nocturnal, and drawn to lights on warm evenings. Most are comparatively small in the tribes Claseini (the smallest tribe with only two genera in South America), Hemigastrini, and Phygadeuontini while the largest tribe, Criptini, includes wasps of larger average size for the subfamily.
Cryptine wasps were pretty common sights for me in the summer of 2017. I had observed many small species, perhaps the same species, in and around a large apiary. The specimen photographed above was found within empty bee equipment in storage inhabited by a few paper wasps Polistes aurifer and the nonnative P. dominula. Whether there was a true association or their proximity was merely a coincidence is left for future discovery. Most cryptines seek out hosts found in soil or in leaf litter, with the exception of the Cryptini which typically seek hosts in foliage.
Acroricnus stylator (tribe Cryptini; Cryptinae)
As previously mentioned, some cryptines use other hymenopterans as hosts. Acroricnus stylator is one such species that seeks out wasp hosts which build mud nests. This includes eumenine wasps such as Ancistrocerus and Eumenes, mud daubers like Sceliphron , and mason bees (Osmia)
Acroricnus stylator (Cryptinae), an individual I caught and later released.
Acroricnus stylator is found in both the New and Old World with various regionally specific subspecies. Adults are known to feed on flowers of the carrot and daisy families. Though they parasitize other beneficial hymenopterans, their presence would suggest healthy host populations.
Xoridine wasps, such as one I discovered on a door under a porch light on a cool late spring morning, are usually hosts of wood boring larvae of beetles (Cerambycidae) and horntails (Siricidae). Some may use other hosts in the Lepidoptera or Hymenoptera, or may be facultatively hyperparasitic.


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.
Meteorus (Braconidae)
Many braconids, such as Meteorus, are economically important to both farmers and gardeners since hosts of these wasps include significant crop pests such as cutworms and tomato hornworms. A few studies have demonstrated that flowering plants increased the lifespans of females, possibly translating into more caterpillars taken as hosts.
Meteorus (Braconidae)
Braconid venom, at least for some species, causes apoptosis (the natural death of cells) around the oviposition site. This could serve to protect the egg, and perhaps protect the young larvae as it begins to feed.
Microgastrinae male captured around stored honey bee boxes infested with greater wax moths
In the summer of 2017, I discovered empty honey bee boxes infested with wax moths (Galleria mellonella) and numerous small cocoons. There were also pteromalid wasps, which I now suspect to be hyperparasitoids of the braconids. The cocoons were likely from microgastrine braconids (possibly Cotesia spp., a common genus). Microgastrines are koinobiont endoparasitoids, mostly on moth larvae. Some species are gregarious, meaning females lay many eggs in a host, while others are solitary.
Silk cocoons of Microgastrinae


The Evanioidea contains three families: Aulacidae, Evaniidae, and Gasteruptiidae. The Aulacidae are parasitoids of wood boring beetles, mostly Cerambycidae, and some Xiphydriidae (Symphyta). The Evaniidae, or ensign wasps, are parasitoids of cockroach egg cases.


The family Gasteruptiidae have unique and easily identifiable abdomens. 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. For instance, I have observed them visiting flowers of onions, Allium cepa.
Gasteruption on parsley flowers in late spring
Larvae of gasteruptiid wasps are predators or predator-inquilines of other hymenopterans 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. Either way, the host larvae dies. Gasteruptiids go through winter as prepupae, then pupate in the spring.


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).
Trichoteras tubifaciens (Cynipidae), crystalline tube gall. This is my best guess as to the identity of this group of small galls. There are very few resources citing this species, which appears to be restricted to a small distribution from Northern California to Southern Oregon.


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 parasitoids, 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.
Galls on the underside of Quercus garryana leaves, likely Cynips mirabilis (the larger speckled gall) and possibly Neuroterus (the small disk-shaped galls).
Gall forming wasps initiate the formation of a gall when certain chemicals excreted by the wasps (or on the egg) make contact with the plant tissue, though the exact mechanism is unclear 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.
Large conspicuous galls, like those of Andricus quercuscalifornicus, are subject to predation from birds. Many galls are at least partially hidden from plain view, or may otherwise be camouflaged in some way.
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.
Cynipid galls with emerged Torymus tubicola (Torymidae). Galls are subject not only to predation, but to parasitism by other insects including other hymenopterans.
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!
Mossy rose gall, Diplolepis rosae
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. They are gregarious, and multiple larvae feed on a single gall, 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. Ichneumonid and chalcidoid wasps have been known to parasitize the larvae of D. rosae.


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).
Torymus tubicola, a parasitoid of cynipid wasp galls.
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?
A very small pteromalid on the tip of a decking screw under high magnification
Some chalcidoids are polyembrionic. Polyembriony in wasps is where a single fertilized egg produces more than one larvae, and some will even produce thousands of offspring within a single host. Copidosoma floridanum (Encyrtidae) typically produces broods exceeding 2000 larvae in a single noctunid host. Some of the siblings will be nonreproductive "soldiers" who patrol the hosts body seeking out competing parasitoid larvae and killing them. Polyembriony is not restricted to the Chalcidoidea, but is also found in a few species in the Braconidae, Platygasteridae, and Dryinidae.
Minimal venation is typical of chalcidoid wasps. This is the wing of a pteromalid under magnificatipon.
In all, chalcidoid wasps attack insects in around 340 families representing fifteen orders, as well as some arachnids (i.e. pseudoscorpions, ticks, and mites) including other hymenopterans. 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).


Torymids are small, often metallic green parasitoids (occasionally phytophagous) wasps sometimes confused with chrysidids. Most are ectoparasitoids or occasionally hyperparasitoids of gall forming hymenopterans (usually Cynipidae), dipterans (Cecidomyiidae), and scale insects (Coccoidea). Species that live in the galls of others may be inquilines, parasitoids, or both entomophagous and phytophagous by feeding on both the gall and the larvae within (similar to some Eurytomidae). Some gall inquilines don't feed on the host larvae, but kill it anyway then proceed to feed on the gall tissue. A few are seed feeders, a unique group which oviposits within developing seeds where the larvae will develop on the tissue within.
Torymus male which emerged from a mossy rose gall, Diplolepis rosae
I have reared, albeit unintentionally, a handful of torymids from cynipid galls of various types. Galls of Cynips mirabilis, a solitary species, have yielded a single torymid per gall. Mossy rose galls, formed by the gregarious species Diplolepis rosae, yielded several torymids of varying sizes and sexes.
Torymus male which emerged from a mossy rose gall, Diplolepis rosae


The pteromalid wasps are mostly ectoparasitoids of Lepidoptera, Coleoptera, and to a lesser extent Diptera and other Hymenoptera (Braconidae). Some are also endoparasitoids or hyperparasitoids, though few if any are phytophagous. Adults only live for a short time, but will feed on nectar, honeydew, or sugary plant secretions. Females require protein for egg production, and host feeding is common. Females typically feed at secretions from the oviposition site, and may even consume some of the host tissue itself. Some species have been described feeding on the eggs of scale insects, as well as serving as biocontrol agents.
Pteromalidae reared from a greater wax moth, Galleria mellonella, under magnification
Pteromalid eggs on a severely weakened greater wax moth larvae
In summer of 2017 I observed and captured pteromalids roaming among greater wax moth (Galleria mellonella) larvae in stored bee boxes. The wax moths had destroyed a great amount of the stored honey bee comb, but there were also many dead moth larvae and Microgastrinae (Braconidae) cocoons. To explore further, I collected several wax moth cocoons to dissect. One contained a severely weakened moth larvae with a dozen small eggs adhered to its body. I placed the larvae in a lidded jar in a temperature controlled room to observe. In two weeks small pupae were developing on the exterior of the larvae with no cocoons of their own, suggesting they rely on the moths own pupal case to protect them. A week later there were adult pteromalids walking around within the jar.


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 information is known about their biology.


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).
Diapriidae with a US quarter dollar
I've observed diapriid wasps on two occasions, both at porch lights in the summer. It may only be a coincidence that their host insects are dipterans, the most numerous insects to frequent my porch lights.


This concludes my observations of parasitoid wasps from 2017. If there is anything I would like you to take from this it is that nature is amazing. And what can you do to protect these obscure yet fascinating creatures? Plant flowers, and try to reduce your use of pesticides. It's that simple. Take notes, photos, and hikes. Watch your porch light at night (a fun way to confuse your neighbors is by staring at your porch light for an hour ion the evening). Who knows, one of us might make some new discoveries. Enjoy your wasps!


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Useful Websites

Microgastrinae Wasps of the
Genera Ichneumonorum Nearcticae American Entomological
Pteromalidae UC
Universal Chalcidoidea Database. Natural History

Special thanks to John Jacob @ Old Sol Bees for letting me use his microscopes.