Sunday, December 13, 2015

Wasps of 2015

Continuing the Pollinators of 2015 theme, I now present to you some of the years flower visiting wasps. Photos are below, but here is a little of what I've learned about wasps:

(Also see Pollinators of 2015 posts: BeesLepidopteraFlies, and Beetles etc.)

Wasps were the predecessors of bees, showing up in the fossil record from the Jurrasic period (~200 million years ago), though they likely evolved over centuries prior to their oldest fossils. The first wasp relatives to appear (in the Triassic) were the sawflies (family Xyelidae), which are considered an ancient wasp predecessor that is still alive today. Sawflies, which are similar to wasps but lack the thin waist of true wasps, do not have a stinger, but instead possess a saw which is used to cut into plants to lay eggs (via an ovipositor). The first true wasps, probably ichneumon wasps and other solitary wasps, were most likely predators and perhaps parasitoids of other insects or plants. It is unclear when these insects, or mutations of them, began visiting flowers for food.

While wasps are generally not celebrated and welcomed like bees and butterflies, they serve an important ecological role and despite the stigma they are quite beneficial. Wasps are closely related to ants and bees, but a few things separate them. Wasps can usually be told apart from bees by their relatively shiny appearance, having less hairs than most bees. Wasps also do not have the pollen holding scopae or other adaptation since they do not collect pollen. Some wasps do have some hairs (like some yellowjackets, though this depends on the species) but the wasp hairs are unbranched while bee hair is usually much more dense and is branched. The result is that unbranched hair allows more light to pass through thus making the wasp appear more shiny. Unlike bees, wasps have straight unbarbed stingers. Bee stingers are barbed so they remain lodged in the threat, pulling the bees entrails out when they fly away (bees can only sting once). This makes sense because bees only use their stingers for defense while wasps need their stingers to hunt, so not dying when hunting is kind of an asset.

While the main diet of wasps, especially wasp larvae, consists of "meat" of some form, the adults feed on a high carb diet of nectar. Adults hunt and kill prey such as other insects (including bees, or meat from your picnic/bbq) to bring back to their nest, chew up, and feed to their young. The wasp larvae, similar to bee larvae who feed on protein-rich pollen, feed on the protein-rich bodies of the prey. Adults do not need the protein, but they do need the carbs attained from sugary nectar to keep up their active lifestyles of flying and hunting until they die. They are most often found on plants with shallow or small flowers with easily accessible nectar since they do not typically have very long tongues. Many plants in the carrot family, in my observations, have been popular with various wasps.

Vespids feeding on Daucus carota
While the most ubiquitous, often infamous, are the social wasps, the majority of them are solitary. This includes potter wasps, cicada killers, tarantula hawks, a large number of parasitic or gall forming wasps, and more. Many of the solitary wasps don't and can't sting (the parasites don't have stingers) but use their stingers, if they have one, for hunting prey.

Wasp nests vary considerably. The most obvious nests are in trees, or the eves of my house. Many more nest in the ground, or in wood. A handful build nests on rocks or man made things out of mud or some other material (mud daubers, for example). The social wasps tend to make a pulp out of chewed up wood fibers and a mix of other materials (plant resin, wasp secretions, etc.). The pulp is then formed into the typical rounded hexagonal cells like honeybees make with wax. Interestingly, the cells are formed as circular cylinders but the force of the adjacent cells turns them into hexagons. If you doubt this then observe the outermost ring of cells, the exposed sides of the cells are round, not hexagonal. Ground nesting wasp nests often have little to show that they are there except for the occasional departure or arrival of a worker. Large nests of some, particularly yellowjackets of the genus Vespula (not to be confused with aerial yellowjackets, genus Dolichovespula, sometimes known as bald-faced hornets depending on the species) can become so large that they come out of the ground and stand taller than a person (see some gigantic nests here).

So enough of that (some of you probably skipped to this point, and that's ok!), here are photos of some of the wasps I've encountered this year:

Family Vespidae

The family Vespidae is one of the most recent wasp families, and likely the most often encountered in the United States. This family includes both social and solitary wasps including hornets and paper wasps.


Likely confused with yellowjackets, this genus is the largest of the social wasps with nearly 250 species.They are considered a paper wasp since they build their nests out of wood pulp and other materials, often in the eves of my house. They form relatively small nests, not the football sized nests of some of their tree-nesting cousins.

Mischocyttarus flavitarsis
Like most wasps they visit a range of shallow flowers like the invasive Daucus and other carrot family plants. Their carnivorous diet includes caterpillars, among other insects. In this way they are very beneficial. For a very complete biography of this particular species (Mischocyttarus flavitarsis), Wikipedia is the place to go: Mischocyttarus flavitarsis. I would suggest reading it, it is quite informative!


Another common paper wasp that forms similar looking exposed cells under the eves of my house is the invasive European paper wasp: Polistes dominula. While there are many native species of Polistes in this country, the European species is probably the most encountered. Compared to the Mischocyttarus above, one can see the two are similar but distinct, particularly in the higher contrast of the Polistes. The two genera mentioned above are very similar in appearance to the genus Vespula, but as in all paper wasps have very thin "waists" (aka the petiole) while the ground dwelling Vespula have short waists with the abdomen and thorax nearly resting against each other. Another characteristic of Polistes is that their hind legs trail behind and below them as they fly, giving them a distinct and conspicuous silhouette while in flight.

Polistes dominula
Polistes dominula
While the paper wasps (and all wasps, for that matter) are generally considered to be threatening and are feared to some extent, most wasps are gentle when foraging on flowers. It is always a good idea to avoid the nests, as most stinging Hymenoptera (aka bees, wasps, and ants) are most defensive and willing to attack if they feel like their nest is threatened. I could have practically pet this wasp, if I was gentle enough. Despite their nonnative status (they arrived sometime around or before 1981, before which they were not recorded in the US), their role in the ecological landscape has some beneficial qualities. At the least they are probably a food source for birds.

Family Cynipidae

Gall wasps are a strange group of non-stinging wasps native to most continents except Antarctica. Their lifecycle is also very strange. Many form galls in oak trees in various parts (leaves, bark, roots, etc.) though the actual gall forming process is a mystery. Roses, maples, and various other plants are used to lay eggs and produce galls. The female wasps lay eggs, and it is speculated that a chemical, either from the parent or from the egg itself, stimulates the growth of the gall from the plant/tree itself (think of a tumor). The developing larvae then feeds on the gall tissue until it is fully developed at which time it will eat its way out and find a mate.

The adults typically live very briefly, sometimes only long enough to mate and lay eggs. As far as I know few or none have functioning mouth parts as adults and thus do not eat after departing the gall. So their role as pollinators is null. They are valuable food sources for birds and other insects in both larval and adult life stages. Insects (including other species of gall wasps) invade and take over the galls of others, laying their own eggs. Birds eat both the developing larvae and the adults.

A few of the galls I've seen here:

Oak apple (Cynips)
Diplolepis rosae on Rosa rubiginosa

I have also seen galls on other plants, but there are other gall forming insects so I was not certain that they were the galls of wasps.

Family Crabronidae

The family Crabronidea (formerly included in Sphecidae) are perhaps the closest relatives to bees, based on recent research (Debevec et al. 2012). This is interesting considering the members of the family Crabronidae are entirely predatory or kleptoparasitic, depending on the species. From a lay mans perspective, I am inclined to agree because my original guess of the subject in the photo below was that it was a bee. Old school taxonomy and classification was based purely on morphology (how it looks), while modern classification systems rely more heavily on genetic sequencing to classify a species. Of course, an expert could identify this as a wasp by looks alone, but I find my original guess interesting due to the recent hypothesis of this group's relation to bees.


Bee wolves, as they are affectionately acknowledged, are predatory ground dwelling wasps. They are solitary, living in deep underground layers up to a meter deep on some species. As the name suggests, they are predators of bees, though the adults feed on flowers. Philanthus seeks out foraging bees and quickly stings them in a vulnerable area such as a joint. The venom paralyzes the bee, but does not kill them. Like other predatory solitary wasps, the paralyzed prey is pulled into the nest and stored alive until it is used (presumably torn apart) to provision the brood cells. Sort of reminds me of how tortoises were used as live meat by sailors before the advent of refrigeration.

Philanthus - Bee wolf
I observed this bee wold near a patch of Trichostema lanceolatum (see the original post here) where very small bees and butterflies were visiting the flowers. This wasp was less than half the size of a honeybee, and had attacked a tiny black bee even smaller than itself. It was hovering over the ground until it aerially tackled the unfortunate solitary bee.

Family Sphecidae

The family Sphecidae, currently in a state of confusion taxonomically, is (for now) placed within the family Crabronidae. Both are evolutionarily recent and probably coevolved alongside bees. Like the Crabronidea, they are predatory, solitary, and sometimes kleptoparasitic.


Ammophila are known as thread-waisted wasps (or sand wasps) of the Sphecidae family. They are solitary ground nesting wasps, preferring sandy soils as the less common vernacular (and the name Ammophila, aka "sand lover" in Greek) suggest. They are nearly cosmopolitan in distribution, being more common in warm regions. They dig unbranched tunnels, bringing prey for the larvae to feed on as needed or bringing figurative banquets for the larvae, presumably depending on the species.

Ammophila on Allium 'Sugar Melt'
Ammophila on Daucus

These are large wasps, nearing two inches long. Like many large pollinators, they are very keen of their surroundings and very distrustful of me and my camera. Adults feed on a variety of plants including Allium, DaucusOriganum, and other flowers of shallow to medium depth. They appear to prefer flowers with more nectar in relation to pollen, no surprise considering few wasps collect pollen.

Family Pompilidae

The spider wasps are an impressive genus of spider hunters. Seeing one of these wasps literally drag a paralyzed spider to its underground nest is not something one can forget, as it is a rather strange and unexpected behavior if you have never heard of it. These wasps actively hunt live spiders to sting, paralyzing the spider but keeping it alive, so they can be kept as a living food source for their developing larvae. A single egg is laid on a single spider and sealed in the nest, dead ants used at the entrance to deter predators by their chemical excretions. The size of the prey appears to dictate the size of the adult, larger prey equating larger adults. Peculiar!

Pompilidae (spider wasp) on Daucus
One of the most conspicuous features of these wasps is their movements. Their wings twitch rhythmically when they are not flying, particularly when they are on flowers, and they move very quickly on the ground (surely an adaptation to keep up with spiders!)

Family Tiphiidae

The flower wasps are another ground nesting parasitoid wasp that feeds on paralyzed hosts in the larval stage. There are few host records, but the known hosts of some of the species are scarabaeoid beetles and mole crickets. The females of most don't have wings, and will become attached to the males while mating as the males continue to visit and feed on flowers.

Flower wasp ♂ (Tiphiid wasp, Subfamily Tiphiinae) on Daucus

Until we meet again!

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