(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.
