|Stelionia male visiting Monardella sp. for nectar|
|Am I ready for my closeup? The face of a bald-faced hornet, Dolichovespula maculata|
|Yellowjacket sting, Vespula pensylvanica, under magnification|
Eusocial bees and wasps inflict not only painful stings, but inflict tissue damage as well. Solitary wasps and bees, by contrast, are often reluctant to sting but when they do it is often weak. But the majority of solitary bees and wasps that are willing to sting, regardless of causing any notable pain or not, do not cause any lasting damage. The significance behind this is that eusocial wasps and bees must protect their nests which are contain their kin, not to mention any food stores they have acquired. Solitary bees and wasps, in contrast, have much less invested into their nests and can usually relocate and build a new nest.
The most hated wasps, it seems, are the yellowjackets. True yellowjackets, Vespula spp., are eusocial ground nesting wasps native to every state of the US and much of Canada. They are easily disturbed and meet any perceived threat with aggression. Their habit of nesting in lawns has brought them too close to home, literally, and are often cause for concern for those with small children or dogs (as a father of two young daughters, I don't blame them! I don't usually condone the killing of wasps or bees, but if one should need to get rid of a nest then wait til the cover of darkness and pour a bucket of soapy water into the nest entrance.) Yellowjackets, like honey bees, live in nests with workers and a single laying queen (excessively large nests of yellowjackets in the southern states may have two or more queens). Queens produce pheromones, much like honey bee queens, which alter worker behavior by suppressing the instinct of workers, all female, from laying eggs. Pheromones also prevent other queens from taking over since they are just ever so slightly specific to each individual queen. Nests are composed of paper, and are structured into several layers of downward facing hexagonal cells in horizontal combs. They hunt all types of arthropods and are also attracted to carrion (or hamburgers). Prey is not stung, but rather bitten apart. What might appear to be stinging is actually just respiration, and the use of the abdomen as an extra limb used to grapple with prey.
Paper wasps are similarly notorious and often interact with humans due to their nesting preferences. Paper wasps nest in elevated and sheltered locations, such as within tree hollows, or more familiarly, under eaves. The nests are made from paper, like all domestic social vespids, but unlike Vespa, Vespula, and Dolichovespula the comb is exposed and not enveloped in a paper shell. Nests are also relatively small, rarely growing larger than eight inches across. In my experience, paper wasps in Oregon are very docile and do not attack except under extreme disturbance (like the time I decided to pry a nest off with a stick). Otherwise, they seem to flee or just fly around rather than stinging. I also find the sting, when it does happen, to be mild compared to honey bees or yellowjackets.
Polistes dominula is a European introduction, now widespread in the West and elsewhere in the country. They are a highly adaptable species and less particular about nesting sites than native paper wasps. There is reason to believe they displace native species by dominating the most favorable nest sites.
|Vespula pensylvanica, up close and personal|
|European paper wasp, Polistes dominula|
|Green eyed Polistes dominula male nectaring on puncture weed, Tribulus terrestris|
|Polistes dominula wing and abdomen under a microscope|
Polistes dominula, and all vespid wasps, have pleated wings. The wings appear thin precisely because the forewings are folded in half when not in flight! This is thought to prevent damaging the fragile wings while in close quarters with nest mates. This trait is also seen in a few solitary bees, flies, and a few other flying insects (all wasp mimics). Most Hymenoptera also have fine hairs covering the wings which may serve multiple purposes including water repellency, reducing drag, thermoregulation, and perhaps other unknown functions. The length and quantity of hairs varies between different wasps and bees, perhaps catering to their varying lifestyles.
Paper wasps, and perhaps other eusocial vespids, visit flowers for nectar which is a source of carbohydrates (necessary for an active lifestyle if you are an adult wasp or bee). Occasionally this resource is brought back to the nest and stored for later use. It was very thick, almost gelatinous and not nearly as viscous as true honey, but was very sweet. A distant relative of the paper wasps, Mexican honey wasps (Brachygastra mellifica) are vespid wasps which build large hanging paper nests in Southern Texas and Mexico. They collect large quantities of nectar and process it into large quantities of a honey like substance. Occasionally the wasp honey is collected, but unfortunately its collection requires the complete destruction of the nest. (By the way, if you happen to have any I'd love to taste it!)
|Honey-like substance in Polistes dominula nest|
|Polistes aurifer, the golden paper wasp, is native to the Western US and Canada|
Some paper wasps use a form of facial recognition to communicate with nest mates and understand hierarchy. Species with less detailed facial patterns do not communicate this way, and instead have comparatively larger olfactory sensors. Polistes dominula, P. fuscatus, and I suspect P. aurifer, are some that have demonstrated facial recognition of nest mates. There is also some speculation that they can recognize the faces of people, though I could not find any literature substantiating that.
|Polistes aurifer (above) and Apis mellifera (below)|
|Mischocyttarus flavitarsis, Western paper wasp|
The largest paper wasps in Oregon are in the genus Mischocyttarus. They are differentiated from Polistes by having a thin elongated waist and reduced front legs, often standing on the center and rear pairs of legs. Nests are similar in appearance to those of Polistes, and my only observation is that they are less abundant than Polistes, while P. dominula is the most abundant. The long legs of all the paper wasps I have observed allow them to land directly on the surface of still water by spreading their legs and utilizing the surface tension.
|Polistes dominula female, magnification showing the waist (petiole)|
The narrowed but not elongated waist of Polistes wasps, as seen in the photo above, allow lay observers to differentiate them from the related Mischocyttarus. Relying on markings and patterns alone is not a reliable method of identification. For example, Polistes aurifer and Mischocyttarus flavitarsis females bear nearly identical markings and patterns in Southern Oregon, though perhaps one or both bear more distinct markings in other regions where different phenotypes take up residence.
|Small mason wasp, possibly an Ancistrocerus spilopterus female (Eumeninae)|
|Honey bee, left, and mason wasp, right for scale|
Eumenine wasps build nests out of mud in cavities, or as freestanding mud pots attached to something off the ground (i.e. house siding, grass, rocks). Many of the eumenines build nests in preexisting cavities such as deserted tunnels in wood or in the case of the above photo in old honey wax comb. Unlike many solitary bees which build linear nests in tunnels, mason wasps are more flexible in the nest structure. Mason wasps cap cells with mud. Potter wasps, however, build external structures that resembles pots with fared constricted entrances. In either case, the cells are stuffed with one large or many small paralyzed caterpillars and an egg, then left to their own devices.
|Ancistrocerus sp. male|
|Showy milkweed, Asclepias speciosa, with a mason wasp|
Mason and potter wasps are common flower visitors. Although they don't provision nests with nectar or pollen like some of the other vespids, adults visit flowers for nectar as it is a readily available source of carbohydrates. Flowers are also occasionally the site of feeding caterpillars or other favorable larvae, so may also be where adult eumenine females might search for prey.
|Ancistrocerus tuberculocephalus male|
Male eumenines do not provision nests, and do not hunt caterpillars. They do visit flowers for nectar, I captured a Ancistrocerus tuberculocephalus male foraging on deerbrush, Ceanothus cunneatus, in late spring. The best thing about the males is that they help create more females! Like all aculeate hymenopterans they can be identified by the extra abdominal segments which enable them to bend their abdomen to mate with females, and for an extra segment in their antennae, often curled at the tip.
|Ancistrocerus sp., a mason wasp|
|Eumenes male, a potter wasp|
The Eumeninae are mostly predatory though a few Eurasian species are phytophagous (feed on plant tissue). Adults usually feed on nectar, or occasionally on hemolymph. Prey is captured for larvae, and is completely or partially paralyzed before sealing in a cell for the wasp larvae to feed on while developing. Species can be generalists when it comes to prey, and take caterpillars or beetle larvae from many families, while others can be more picky to the point of only taking prey of a single genus of moth or leaf beetle larvae, for example. Number of prey can also be variable for some species, such as one large prey item or several smaller prey items per cell. This variability is also found to be common in the Sphecidae and Crabronidae.
|Stelionia sp. female visiting Echinacea purpurea|
|Bembix americana female exiting her nest|
|Bembix americana hovering above her nest entrance|
|Steniolia sp. female visiting Echinacea purpurea|
Steniolia dig nests in soil rather than sand, but are otherwise very similar to the sand wasps. I have also observed them to be slightly larger than Bembix, at least the species I've encountered. Nests descend six to seven inches ending in a single cell which, like Bembix, is provisioned progressively with flies as the larvae develops. Both genders of the genus cluster at night to share warmth, which is also when mating occurs (I haven't observed this, but I'd love to some day).
|Steniolia male visiting Monardella sp.|
I found Philanthus gibbosus nesting in near vertical banks along Evans Creek near the Rogue River. Sand wasps (Bembix americana) and osmiine bees were also nesting in close proximity. Some species of Philanthus are known to share a nest entrance but continue to provision their own nests within. Philanthus females are also known to line their cells with microbes which protect the developing larvae from potential pathogens. I wonder if this behavior occurs in other types of wasps or bees, yet awaits discovery.
|Ectemnius sp. visiting Daucus carota|
|Ectemnius sp. in the subalpine zone on Mt. McLoughlin|
|Tachytes sp. visiting narrowleaf milkweed, Asclepias fascicularis|
|Tachytes sp., chilled not killed|
|Aphid wasps, Stigmus sp.|
|Aphid wasps, Stigmus sp.|
This concludes Part 1, follow the link to continue to Aculeate Wasps of Southern Oregon Part 2 which will include photos and bios of many lesser known aculeate wasps!