(This is Part 2 of Aculeate Wasps of Southern Oregon, see Part 1 by clicking here)
Cuckoo wasp, Chrysis sp.
Wasps are amazing. I love the wasps that everyone (in the colloquial sense) hates, yellowjackets, hornets, and paper wasps. Vespid wasps are probably the most evolutionarily advanced of the wasps, since in the Hymenoptera eusocialism appears to be the trend. The wasps that truly fascinate me are the hundreds of thousands of solitary predatory and parasitoid wasps that live their lives without much notice. The lives of the solitary wasps are so incredibly diverse there is no vertebrate comparison. What I present to you is but a small sampling of aculeate (stinging) wasps I have encountered in Southern Oregon. The term "stinging wasps" is conflicted because not all are capable of stinging people. Older lineages of wasps (the true parasitoids) did not possess stingers but rather had ovipositors. Ovipositors are elongated egg-laying apparati used to lay eggs on or within a host, such as a caterpillar. Aculeate wasps differ from their ancestral relatives, since their ovipositors have evolved into stingers. Venoms which initially were used to paralyze hosts now possess pain-inducing molecules, among other things. As stated previously in Part 1, most solitary wasps are reluctant to sting, and are practically harmless. Don't kill them.
Sphex lucae visiting wild carrot, Daucus carota
Sphecidae
The Sphecidae are solitary wasps which are easily differentiated from the Crabronidae by the elongated first abdominal segment, giving rise to the common name thread-waist wasps. Most of the wasps are predatory, while a small percentage are kleptoparasitoids which will take food from others for their young. These wasps may seem daunting to some, but they are hard pressed to sting. Even after handling several, even attempting to get stung (who does that?!), I was disappointed when they fled or just wouldn't sting me, those jerks. Being solitary wasps, their sting is better adapted to stinging soft bodied larvae or thin membranes between the plates of armored prey than stinging an annoying human.
Ammophila sp.
Ammophila adults are commonly seen visiting flowers where they are native. Females dig underground nests with a single cell chamber, occasionally two. They prey on moth caterpillars or caterpillar-like sawfly larvae, which are paralyzed by the sting of the female, and then dragged into the nest. Sometimes many small caterpillars are progressively delivered to the growing larvae, but more often a single large caterpillar is deposited with an egg and the nest is sealed for good until the new wasp emerges. One particular trait of these wasps is that they like to disguise their nests after they are sealed, or even before they bring prey or lay eggs. I once watched as a large female brought small pieces of bark, or large in relation to the wasp, to conceal a nest entrance. This behavior may discourage would-be predators or parasites from finding the precious larvae.
Ammophila sp.
Ammophila, like other predatory sphecids, have large powerful mandibles. Their heads may also be big, correlating to the size of their preferred prey, since the muscles that allow them to carry their prey are in their heads.
Ammophila sp. in the subalpine zone of Mt. McLoughlin
When I climbed up Mt. McLoughlin in August, I found Ammophila in the subalpine zone, just above the tree line. Ammophila prefer to nest in sandy soil, and that is what is found up there. Soils high on mountains are usually rudimentary, high in mineral content and low in organic matter, and perfect for many ground nesting wasps and bees (both of which were highly active during my hike on Mt. McLoughlin).
Sceliphron caementarium
Black and yellow mud daubers are just as familiar or more familiar than Ammophila, but are probably more recognizable for their nests than the wasps themselves. Mud daubers build mud nests on exterior surfaces, and they aren't picky about what kind of surface. However, they have an affinity for hidden and protected nesting places such as inside empty bee hives or under siding. They have even been known to attach nests to airplanes or shipping containers, and are currently found in every continent except Antarctica, including many remote islands. Nests are usually found close to sources of mud such as rivers or springs. This is in contrast to potter wasps (Eumeninae) which create their own mud by collecting water and mixing it with fine mineral medium to create their urn-shaped nests. Nests in different regions vary based on the locally available mineral composition of the available mud. Mud nests survive best in protected niches because rain can severely weaken the mud and put the developing wasps at risk, though from the prepupal stage the wasps surround themselves in a cellophane-like casing which is at least partially water resistant (personal observation).
Sceliphron caementarium
Mud dauber nests are formed from a grouping of one to several cell chambers, coated in totality in a protective layer of mud. Parasites and parasitoids infiltrate the mud nests despite the best efforts of the nest builder. Various fungal and (assumed) bacterial infections kill developing larvae and pupae, as well as death of larvae and pupae by kleptoparasitic or predatory interlopers (including other hymenopterans and vertebrates). Survival of developing mud daubers is hindered by these pests but countered by the many eggs laid per female each year, at least 25 cells in large nests (possibly multiple nests per female). I have often found that even in heavily infested nests, at least one or two larvae survive.
At the end of 2016 I collected several S. caementarium nests. Several had begun to hatch out, so I broke one apart to reveal the wasps in their pupal casings. In normal circumstances the wasps have to chew their way out of the cellophane-like casing and then proceed to chew their way through the wall of the mud nest to escape. In this situation I observed a young wasp that was very active within the casing, while the others were visibly inactive and presumably not mature enough to emerge yet. Perhaps it was the warmth of my hand, or maybe just by chance, but I was extremely fortunate to observe a mud dauber emerge for the first time. I was nearly overcome with emotion reminiscent of the birthing of my two daughters. A life had emerged into the world for the first time, and it moved me.
Contents of Sceliphron caementarium nest
Black and yellow mud daubers prey on spiders, usually orb weavers and crab spiders (varying regionally, I suppose). As many as fifteen spiders will be captured, paralyzed, and stuffed into each cell for the developing larvae to feast on. I dissected a nest and discovered the spiders pictured above, mostly crab spiders (Thomisidae). They were all presumably alive, and a few could move but only slightly, the venom apparently having either worn off or not being fully effective from the beginning. I discovered larvae in different stages of development, different instars. S. caementarium is multivotine, meaning they have multiple generations per year, and that nests are prepared all year long so long as the climatic conditions are favorable. I placed these larvae, and spiders, into a small closed wooden box (~1 square inch) and upon inspection a month later discovered webbing suggesting at least one of the spiders had regained enough mobility to spin silk. I wonder if, despite the shortcomings of the venom or maybe misplacement of the sting, spider prey is kept from harming the wasp larvae by the immobilizing affect of cell confinement.
Great golden digger wasp male, Sphex ichneumoneus, visiting narrowleaf milkweed, Asclepias fascicularis
The great golden digger wasp is a common sphecid native to nearly all of the lower 48 states, parts of Canada, and Mexico. As the name implies, the species is ground nesting. Up to six katydids are paralyzed and placed into underground cells. Birds, particularly house sparrows (Passer domesticus) have been observed (not by me) to startle digger wasps forcing them to drop their katydid prey, whence the birds claimed the katydids for themselves. A small percentage of females will forgo the creation of their own underground nest and proceed to provision another digger wasp nest, saving the labor of digging the nest herself. Females provision the same cells instead of just share the same nest entrance. Similar behavior in ancient wasps is theorized to have been a precursor to hymenopteran eusociality. If the joint nest mates should ever meet they will fight, but if they never encounter one another whoever lays the first egg and seals the nest will "win" the nest while the other is forced to dig her own nest or forfeit her reproductive success.
Sphex lucae visiting wild carrot, Daucus carota
Another species of Sphex (less studied) native to the Western states (From WA in the north, south to CA, east to TX). Sphex are known to prey only on katydids (Tettigoniidae), and each species of wasp preys on a single species of katydid. The wasps themselves have been known to be hosts to twisted-wing parasites (Strepsiptera). Strepsiptera are true parasites, wingless females live their entire lives embedded between abdominal tergites of many hymenopterans. Sphex are also victim to various nest parasites, yet some species are known to build false burrow entrances (accessory burrows) to mislead and distract interlopers from the true nest. Some crabronids (i.e. Bembix and Philanthus) are also known to dig accessory burrows. Ammophila, another ground nesting sphecid, misleads would-be nest invaders by depositing excavated soil away from the nest entrance.
Grass-carrying wasp female, Isodontia sp., visiting parsley flowers
Many wasps are fairly inconspicuous when creating nests. Not Isodontia, known as grass-carrying wasps, a tip of their preferred nesting material. Isodontia are cavity nesting wasps which use large chunks of grass to separate cells and cap nest entrances, and are often seen carrying pirces of grass larger than themselves. Their typical nesting sites are hollow stems, but they will also nest in other cavities in wood, or in some cases, umbrella poles (or other manufactured human things). Their prey are Orthoptera, typically Gryllidae or Tettigoniidae. One to twenty prey items are placed in each cell, varying between species of wasp and probably the size of the prey.
Prionyx sp. (atratus or subatratus) on rabbitbrush, Ericameria nauseosa, on Upper Table Rock
I discovered an individual Prionyx (either atratus or subatratus, the only all black Prionyx in the US) late in the day visiting a rabbitbrush plant at the summit of Upper Table Rock. The sun was setting and the wasp seemed to be wandering around on the shrub for no particular reason. Like some of the other sphecids I've showcased, Prionyx preys on Orthoptera, particularly short-horned grasshoppers (Acrididae), taking both older nymphs and adults. They usually capture and subdue prey, paralyzing it with its sting, then proceed to excavate a burrow after prey is acquired. A single cell is created at the end of each burrow. A single prey item is normally delivered per egg/cell, since chosen prey are typically large in relation to the wasp.
Pompilidae
Calopompilus pyrrhomelas visiting threadleaf milkweed, Asclepias fascicularis, at the base of Lower Table Rock
Some of my personal favorite solitary wasps are the spider wasps, or pompilids. I love all the wasps, but spider wasps are rock stars! Most pompilids hunt spiders, normally taking them head on, paralyze them, drag them into a hole, and seal them in with an egg. The living spider is eaten while the wasp sucks the life force right out of it. Another notable feature is that the sting of some pompilids is known to be very painful, the most painful hymenopteran sting award going to the large tarantula hawks (Pepsis spp.) of the American Southwest. Despite the pain, practically no lasting damage is done (except maybe for a damaged ego), as opposed to eusocial wasps and bees whose venom breaks down cell tissue and other unfortunate effects. I haven't been stung by any of the spider wasps, though it is truly on my wish list.
In Southern Oregon the largest pompilid I've encountered is Calopompilus pyrrhomelas, a smaller cousin of the tarantula hawks. They prey on a single spider species, as most spider wasps do. This spider wasp takes folding-door spiders, Antrodiaetus (probably A. pacificus), but is said to face them directly in the spiders own burrow. If the wasp is successful, the spiders burrow becomes its grave and the wasp adheres an egg directly between the spiders legs and seals the cell. The spider, doomed, and a new wasp lives. Calopompilus is seldom found on flowers, though they may have an affinity for milkweeds like their larger cousins in the South (some milkweeds may be primarily pollinated by large wasps, like pepsine wasps), and also for rabbitbrush (Ericameria nauseosa) as the host records demonstrate.
Auplopus sp.
Most pompilids nest in the ground, but a few nest in nests constructed above ground. Auplipus create mud nests, a jumble of mud cells, in protected locations such as under leaves or siding, or more often in preexisting cavities created by beetle larvae or other wasps. Some may even nest in abandoned mud dauber nests. Some species remove the legs of their spider hosts in order to feed on the hemolymph, or to make transport of the paralyzed spider easier. Eric Eaton has written a nice piece on these wasps, see it here.
Evagetes sp. in the subalpine zone on Mt. McLoughlin
It seems that the deeper one delves into the world of wasps, the more one must expect the unexpected. Many hymenopteran families have their very own black sheep, and Evagetes (Pompilinae) is one of the black sheep in the Pompilidae. They are social parasites, or kleptoparasites, who lay their eggs in the nests of other pompilids. Pompilids in the subfamily Ceropalinae are also known to be kleptoparasites, as well as paper wasp (Polistinae) mimics.
Evagetes sp.
Female Evagetes seek out completed pompilid nests, perhaps of a specific host species. I am not clear how this is done, perhaps by a scent or some other means. When a host nest is discovered, the female digs down into the chamber with the spider and host egg. Sometimes the egg is destroyed by the parasite, other times the host egg is eaten by the Evagates larvae which hatches prior.
Mutillidae
The mutillids are often confused for ants, since the females are hairy and wingless. The common names offer no help names such as "velvet ant" or "solitary ants". They can be differentiated from ants, which have one or two nodes between the mesosoma and metasoma, absent in wasps and bees. Another common name, "cow killer", is usually reserved for a single species, Dasymutilla occidentalis, which is known to have a very painful sting.
Dasymutilla sp. female
Female velvet ants are ectoparasitoids or kleptoparasites of a variety of other wasps, bees, and perhaps ants or their inquilines. Some mutillids are nocturnal, while the majority are probably diurnal. The combination of their painful sting, bright colors, heavily armored bodies, and an assortment of other aposematic defenses means they are usually left alone, even when boldly trekking across bare ground. Most are parasitoids of solitary unguarded larvae or their provisions, but some seek hosts within social nests of halictid bees or even honey bees in some European species. In the case of eusocial hosts, the wasps make their way through the bee guards, by just walking right in or killing them, and parasitizing the closed cells containing young pupae. An egg is laid, and the mutillid larvae feeds on the host pupae until pupating itself.
Mutillidae male
Male mutillids often look nothing like their female counterparts. They can be so different than females in appearance that some have even been wrongly classified as different species. Males also look suspiciously similar to wasps in the families Bradynobaenidae and Chyphotidae, though none are closely related.
Sapygidae
Eusapyga sp.
Sapygid wasps are Batesian mimics of eusocial Vespidae, though much less commonly encountered. They are ectoparasitoids or kleptoparasites of bees, mostly in the Megachilidae, though a few host records reveal eumenine wasps as hosts to some genera outside the US. Typically the newly hatched first instar sapygid larvae, which hatch prior to the host egg, puncture and consume the contents of the host egg (known as hospicidal behavior) before feeding on the provisions provided by the host (i.e. pollen).
Eusapyga sp.
Sapygids visit flowers, mostly Apiaceae and Asteraceae where nectar is often easily accessible. Like other parasites and predators of bees, flowers are often not far from nests of hosts. Megachilid bees, the most common hosts, also tend to visit flowers with easily accessible resources. I have never personally seen (or was aware of) sapygids visiting flowers. I had found one near a large apiary, a place I have observed several species of megachilid bees including Megachile and others.
Chrysididae
Chrysis sp.
The Chrysididae is a large and varied family with common names such as cuckoo or jewel wasps, for the life styles or physical appearances of some, respectively. They are unique among the Hymenoptera by possessing a specialized ovipositor which evolved solely within the Chrysididae. The ovipositor, much unlike the parasitic Ichneumonidae and related parasitoids, is made from the last several segments of the abdomen and is telescoping. Some chrysidids are kleptoparasitic, laying eggs in the nests of other hymenopterans to feed on their stored provisions (and killing the host larvae), or true parasitoids by feeding on the larvae or pupae of a host (i.e. pupating moths).
Chrysis sp.
Most chrysidids lack the ability to sting, and rely on their stout and heavily armored bodies as defenses against stinging hosts. Many of the larger species are metallic blue, green, or sometimes red, while smaller species are dark metallic green or black. They can sometimes superficially resemble torymid wasps (Torymidae), blow flies (Calliphoridae), or some bees (metallic green bees in the Halictidae and Megachilidae), but the short legs and antennae on chrysidids is somewhat distinguishable to the trained eye.
Chrysis sp. visiting Daucus carota
Chrysidid adults visit some flowers for nectar, most notably flowers in the carrot family (Apiaceae) which have many small flowers in clusters with easily accessible nectar.
Bethylidae
Epyrinae
Bethylids are very small wasps related to the chrysidids. They are ectoparasitoids of beetle or moth larvae. Females possess stings which they use to permanently or temporarily paralyze hosts so they can attach an egg to the hosts body. In the case of some larval hosts, female bethylids have been observed removing hairs from the hosts body in order to achieve good egg adhesion. Bethylid larvae sometimes live part of their lives as ectoparasitoids, but in later instars become endoparasitoids and finish off the host from within. Female bethylids sometimes feed on the hemolymph of the host, even killing them. This behavior may contribute to the fitness of the females, increasing their egg laying capacity. Depending on the species, females may lay between 50 and 100 eggs in their lifetime.
Epyrinae, with a US quarter for scale
I discovered the bethylid pictured above inside a highly active honey bee hive. The small wasp, nearly the size of the antennae of the much larger honey bees, was completely ignored until I caught sight of it. Some bethylids are known hosts of Cucujoidea or Pyralidae, the families containing hive pests small hive beetles (Aethina tumida) and greater wax moths (Galleria mellonella), respectively. Bethylids are also parasitoids of certain house pests, such as carpet beetles (Dermestidae).
Tiphiidae
Paratiphia sp. visiting Daucus carota
Tiphid wasps, sometimes known as flower wasps, are parasitoids of ground nesting beetles (mostly Cicindelinae and Scarabaeoidea) as well as some ground nesting bees and wasps. Host larvae are temporarily paralyzed, then eggs are attached to the underside of the host. Adult females sometimes feed on the host themselves in order to supplement their diet of flower nectar and honeydew.
Paratiphia sp. visiting Daucus carota
There are many more species of wasps in Southern Oregon, many that I haven't encountered myself. This is good, because it leaves the future to discover these treasures and refresh my always growing love and passion for wasps and other hymenopterans. Return soon and learn about the fascinating and more primitive parasitic wasps, such as the ichneumonids, diapriids, and pteromalids! Also to come, more bees! Stay tuned while I try to keep the approaching winter from being boring and drab.
Wasps have a bad reputation. Ask ten people what they think of wasps and seven of them will tell you they do not like wasps. This is what I learned after I created a survey earlier in 2017 (simply entitled Wasps. You can still participate in the survey here). The survey was distributed via social media, email, and word of mouth. The majority of the participants considered themselves to be nature enthusiasts and gardeners, though academics and beekeepers also made up a large percentage, and lastly a small percentage considered themselves none of these things. Although the survey had some issues, and lacked some of the qualities of a professional scientific study, what was clear was that wasps as a whole are not viewed in the best light. This was reinforced in the end of the survey, when I allowed participants to write a comment relating to wasps. Some of the comments showcased knowledgeable participants who noted the beneficial aspects of wasps, including the non-stinging parasitoids (not featured in this article), and the non-aggressive nature of many of the solitary wasps. Most of the responses, however, were less pleasant with comments like I like bees but not wasps or yellowjackets are a**holes. My mission is to confront the prejudice and lay out the reality of wasps which is both fascinating and occasionally obscure (and oh so alluring to me). There is much to learn of wasps.
Spider wasp, Evagetes sp. (Pompilidae) with relatively long sting. Despite the intimidating appearance of the sting, these wasps are far more likely to flee than try to sting, even when I captured one with my hand. Evagetes are kleptoparasitoids of other pompilids, and do not build their own nests.
Being stung is likely the primary concern most people have regarding wasps. When it happens, it can be painful and unpleasant. Stings from bees and wasps can instigate allergic reactions ranging from itching and swelling, hives, or on rare occasions, life threatening asphyxiation. The CDC attributes around 100 deaths per year in the US to stings by insects and other arthropods (i.e. scorpions), though other sources estimate 50 deaths a year, which is one out of every six million people in the US (or one out of every three million for all stinging deaths). This doesn't discern whether the deaths were a result of allergic reaction. One common misconception is that for those who are allergic to honey bee stings they are also allergic to stings from wasps. Venom chemistry is complicated and differs significantly between wasps and bees, as well as many considerable differences between the venoms between different species of wasps, bees, and ants. No two are exactly alike, and most are dramatically different. That said, being allergic to both honey bee and paper wasp stings, for example, is extremely unlikely. For more on the science of stinging Hymenoptera and venom, I encourage the reader to see the work of entomologist and researcher Justin Schmidt.
Eusocial Vespidae
Am I ready for my closeup? The face of a bald-faced hornet, Dolichovespula maculata
The most notorious, or rather infamous, of all wasps are the wasps in the family Vespidae. This family includes eusocial wasps such as yellowjackets (Vespula), aerial yellowjackets (Dolichovespula), true hornets (Vespa), and paper wasps (Polistes and Mischocyttarus), as well as an array of non-aggressive solitary wasps. These wasps interact with people in a variety of ways, nesting under eves in the case of the paper wasps, nesting in lawns in the case of yellowjackets, or in all cases crashing your picnic or BBQ party. Social vespids are all predatory. Usual prey include flies, caterpillars, and many garden pest species, but they may also hunt larger arthropods or be attracted to carrion. Unlike the solitary vespids, chewed up pieces of the prey are brought back to the nest rather than a complete paralyzed yet living prey item.
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.
Vespula pensylvanica, up close and personal
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.
European paper wasp, Polistes dominula
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.
Green eyed Polistes dominula male nectaring on puncture weed, Tribulus terrestris
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.
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.
Honey-like substance in Polistes dominula nest
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!)
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)
Unlike yellowjackets and hornets, paper wasps are not aggressive towards honey bees. This is a concern for some beekeepers I have spoken to who attempt to justify their general prejudice towards wasps as a whole. In general, keeping honey bee colonies strong by the proper care and attention (i.e. IPM, feeding as needed, good genetics, etc.) will keep any wasp threat from subjugating the hive. Weak colonies are not well equipped to defend their home, thus thieves or predators may freely enter. Paper wasps, unlikely to prey on honey bees themselves, will rob honey from weak or dead colonies. I would argue that the wasps are merely a symptom, but not the cause, and actions should be taken to build up the strength of the hive rather than eliminating the perceived wasp threat.
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.
Solitary Vespidae
Small mason wasp, possibly an Ancistrocerus spilopterus female (Eumeninae)
Solitary vespids are often very similar in appearance to their eusocial and semi-social (and usually more aggressive) cousins. The Vespidae contains five subfamilies, two are eusocial or semi-social (Vespinae and Polistinae, respectively) while the remaining are solitary. So far only known in California, the Euparagiinae is rare. I find the Masarinae to be particularly interesting as solitary females provision mud nests with pollen rather than insects. Maserine wasps collect pollen in their crop and regurgitate it into the nest, similar to masked bees (Hylaeus spp., Colletidae). The genus Pseudomasaris (Masarinae) is known to occur in Southwestern Oregon, though I have not seen one yet (to my knowledge). I'm keeping my eyes out, they are active in early summer and superficially resemble yellowjackets.
Honey bee, left, and mason wasp, right for scale
The Eumeninae is the most common of the solitary Vespidae. In general they are smaller than their eusocial cousins, but many bear a superficial resemblance with yellow and black patterns. Others have patterns that are black with either red, white, or orange. Despite their similarity to their occasionally aggressive extended family, the solitary vespids are quite reluctant to sting and will swiftly flee if a threat is perceived. Those who have managed to somehow get a sting from one of these wasps report disappointment in such a weak defense. Their first line of defense is aposematic, the bright showy colors resemble yellowjackets or other vespids with painful stings.
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
In 2016 I collected some mason wasp nests built in old honey bee comb to rear them and attempt to identify what emerged. Wasps begun to emerge as early as February (2017), starting with male Ancistrocerus as seen on my finger in the above image. Eumenine wasp eggs hatch shortly after they are deposited, within days to weeks, and quickly devour their paralyzed caterpillars. They enter winter as prepupae and remain that way until pupating the following year. I suspect temperature plays a large role in their pupation and emergence. At the time of the emergence of those first few Ancistrocerus males, there was still some remnant snow on the ground in the Rogue Valley. Secondly, the screened jar which held the nest was in my truck where it surely experience higher mean temperatures than outside, not to mention much drier conditions.
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
Many observers have noticed that eumenine wasps have different types of nests, within cavities or as external structures. Common names serve to delineate them by nest type, yet, there is no well known taxonomic distinction between mason and potter wasps that I am aware of. I have observed them to be morphologically distinct, however, as they can be distinguished by differences of the petiole. The mason wasps that I am acquainted with have short petioles (see photo above) while potter wasps have an elongated petiole (see photo below) much like Mischocyttarus.are in general slightly larger than the mason wasps.
Eumenes male, a potter wasp
Perhaps the common names mason and potter wasp are not scientifically significant, though they do serve to describe the Southern Oregon species fairly. In my observations various eumenines are active from spring to fall, suggesting that many may be multivoltine, that is, having multiple generations throughout the year so long as good conditions prevail.
Eumenes verticalis
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.
Crabronidae
Stelionia sp. female visiting Echinacea purpurea
The Crabronidae is thought to be closely related to the bees, the latter having evolved from the former. Ironically, some crabronids prey primarily on bees and other hymenopterans. Many crabronids are even mistaken for bees as they share some superficial traits. Having been fooled myself, I am certain of this. The Crabronidae prey on a wide variety of other insects and spiders. Prey are usually paralyzed and brought back to the nest for larvae to feed on.
Bembix americana female exiting her nest
Sand wasps in the genus Bembix are widespread in Oregon. They are called sand wasps because they nest directly in loose sand. I observed them on a sandy bank alongside Evans Creek (which meets the Rogue River) where a layer of hard packed silty soil formed a layer a few inches below the sand. The nest entrance itself fills with sand when the wasp isn't actively entering or exiting, so often appears as a small divot in the sand. Sand wasps are great diggers, diving into the sand with great ease, casting particles of sand behind them as one might imagine a digging dog.
Bembix americana hovering above her nest entrance
Bembix prey on flies, and don't seem to be specific about which types. Flies are paralyzed with venom and brought into the nest. Bembix provision cells progressively as their larvae develop, delivering up to twenty flies for each larva. Bristly hairs on their legs allow females to dig through sand with the two front legs while carrying prey with the remaining legs.
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.
Steniolia have very long tongues (probosces) when compared to other wasps, longer than many bees too. They have a particular interest in violet colored flowers such as thistles, some monardellas, and purple coneflower. Alternatively they are also known to be drawn to orange, yellow, or occasionally (but far less frequently) white flowers. Males can't sting, but are equipped with a double pronged pseudosting at the tip of the abdomen. Crabronids in general are quick and will readily flee if danger is perceived, but I hypothesize that if I were to capture a male with my hand he would poke me quite hard, perhaps hard enough to make me release him as a reaction. I have experienced a similar reactionary response when handling male wasps of all kinds who simply motion as if to sting, sans the pseudosting. Fear of being stung is powerfully integrated into the human psyche.
Philanthus gibbosus
Beewolves, Philanthus spp., are one of my favorite genera of all wasps. As much as I love bees, this bee-predator has charmed me. Beewolves are a group of ground nesting wasps which, unlike Bembix and Steniolia, mass provision cells before laying an egg and sealing the cell. Their primary prey are small bees, mostly but not strictly halictid bees (possibly a result of the abundance of halictid bees, some of which are semi-social), however beewolves are known to prey on other wasps and even occasionally other types of insects as well. Up to two dozen prey items will be packed into each cell before an egg is laid.
Philanthus gibbosus
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 wasps prey on flies, mostly hover flies (Syrphidae). Unlike the aforementioned crabronids, Ectemnius nest in dried twigs or stems with soft pithy centers, or in holes in dead or decaying (soft) wood, varying between species. Cells are made from chewed pith and stuffed with flies, or maybe few to single large flies, depending on the species.
Ectemnius sp. in the subalpine zone on Mt. McLoughlin
In August of 2017 I hiked to the alpine zone of Mt McLoughlin halfway between Klamath Falls and Medford. I was fortunate to photograph Ectemnius nectaring on an unknown carrot relative (Apiaceae). Many other hymenopterans were active, from small halictid bees to sphecid wasps, pompilids, and chrysidids. Numerous dipterans (flies) were also active. Alpine and subalpine environments exhibit more extremes than lower elevations (i.e. climate), and life up there has evolved to survive the unique challenges presented. Plant life in the alpine and subalpine zones is particularly interesting, though notably more sparsely dispersed than the lowlands. This may lead one to think that life is less diverse in the mountain ecosystem, but that is a fallacy. Pollinators are quite numerous in the alpine zone, though not the same mix of pollinators found in the lowlands. Flies are very important pollinators of alpine and tundra environments since they are better able to cope with poor weather conditions, though many types of bees and wasps also flourish when the weather is favorable.
I had originally mistaken this square-headed wasp for a honey bee, because honey bees were foraging on the milkweed in great numbers and the wasp was of a similar size and shape. Tachytes nest in the ground and provision each cell with Orthoptera adults or nymphs, primarily grasshoppers or katydids. Prey selection is somewhat specific depending on the Tachytes species. Some will provision every cell with a prey item before laying any eggs, temporarily storing the orthopterans in a special chamber off to the side while chambers are being excavated.
Tachytes sp., chilled not killed
Like many crabronids, this Tachytes was difficult to observe. To get a better look, and have a good chance of having it identified, I captured this wasp with an insect net and placed it in a jar. I placed the wasp in the refrigerator for ten minutes. The wasp was then chilled and temporarily immobilized, allowing me to get a good look. I brought it outside into the sun so it could warm up, after which it promptly flew off. This is a good technique for viewing many hymenopterans up close, though make sure to release the specimen as close as possible to where it was captured so it may carry on.
Aphid wasps, Stigmus sp.
Aphid wasps (Pemphredoninae) earn their name for their choice of host. Nests are constructed within existing holes in wood and mass provisioned with aphids. Don't confuse them with the other aphid wasps, Aphidiinae (Braconidae), which parasitize the aphids by laying an egg inside them.
Aphid wasps, Stigmus sp.
Initially I had confused these aphid wasps for masked bees, Hylaeus spp. (Colletidae), since they both lack pollen collecting hairs and are similarly small, less than 6mm in length. They are also both common visitors to wild carrot flowers, Daucus carota, an invasive weed here in Southern Oregon.
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!
