Another Micro Mystery

One way that I find insects in winter is by scraping off paper wasp nests that have been abandoned by the past season’s generation of wasps, and placing the nests in a transparent container. What usually happens is that one or more kinds of insects will eventually emerge from these nests. Allow me to share one example.

Dibrachys sp.

I started collecting recent, abandoned paper wasp nests (Polistes metricus is the common species around our home here in Leavenworth, Kansas, USA) when I saw a social media post by Sloan Tomlinson (@thatwaspguy on Instagram). He had reared a type of small parasitoid wasp as a result: the eulophid wasp Elasmus polistis. That species is a parasitoid of the brood (larvae, pupae) of paper wasps. Cool. I could add another species to my home biodiversity list.

So many tiny wasps!

I was excited to find, in January of 2022, that this method had worked, as I saw tiny wasps running around inside the container with the old paper wasp nest. Photographing the little creatures, and then cropping those images, it became apparent that what I had was not what I expected. I was left with a mystery that took me awhile to solve, even though I’m fairly good at researching.

I eventually found a journal article chronicling a study of various parasitoids of paper wasps collected from nests in Missouri, the state immediately adjacent to Kansas. In fact, Leavenworth is right across the Missouri River from Missouri. One of the creatures listed was a wasp in the family Pteromalidae. They had only eighty-seven specimens, though. I was looking at hundreds by the time they finished emerging.

Male wasps attempting to mate with a female.

The species name given was Dibrachys cavus. More recently, it has been revealed to be a “species complex,” and has a new assigned name: Dibrachys microgastri. It represents one of *three* species, any one of which could potentially be my creature. Collectively, they are parasitoids of pretty much any insect with complete metamorphosis. That makes it difficult to determine exactly which one I have. Even placing a specimen under a microscope might not be enough magnification for these two-millimeter wasps.

Dibrachys is unusual for a single genus of wasps in having such a wide range of potential hosts. At least some species, or perhaps most, are hyperparasitoids of tachinid flies and braconid or ichneumon wasps that are themselves parasitoids of moth pupae. This makes me wonder if these minions are part of this puzzle that I documented in 2022.

I find unsolved mysteries intriguing, and delight in them even if I never reach any verifiable conclusion. There will always be *something* that defies explanation in the natural world.

This little cobweb weaver spider may have been making a killing, literally.

Sources:Gibson, Gary A.P., John T. Huber, and James B. Woolley (eds). 1997. Annotated Keys to the Genera of Nearctic Chalcidoidea (Hymenoptera). Ottawa, Ontario: NRC Research Press. 794 pp.
Peters, R.S. & Baur, H. 2011. A revision of the Dibrachys cavus species complex (Hymenoptera: Chalcidoidea: Pteromalidae). Zootaxa, 2937 (1), 1-30.
Whiteman, Noah K. and Brett H.P. Landwer. 2000. Parasitoids Reared From Polistes (Hymenoptera: Vespidae: Polistinae) Nests in Missouri, With a State Record of Elasmus polistis Burk (Hymenoptera: Elasmidae). J Kansas Ent Soc 73(3): 186-188.

Wasp Wednesday: Walden's Mason Wasp, Ancistrocerus waldenii

Guest post by Heather Holm

The Vespidae subfamily Eumeninae includes primarily solitary wasps that nest aboveground in pre-existing cavities (hollow stems or brambles, holes in wood) or in free-form mud nests. One morphological trait eumenines share with the social wasps also in the family Vespidae, is wings that fold longitudinally. Eumenines (potter and mason wasps) are generally black with white, rusty orange, and/or yellow markings. In the southeastern United States, some species have very prominent red markings and in some instances, these red markings replace the white or yellow markings of northern populations. Generally, eumenines hunt various families of moth larvae (caterpillars) although a minority prey on beetle larvae.

Potter and mason wasps use mud to line, partition, or construct their solitary nests. For those that nest in pre-existing cavities, partitioning the cavity with mud results in individual cells or rooms in which a single larva develops as it feeds on the cache of prey provided by their mother. Free-form mud nests are either single-celled (ex. potter wasps in the genus Eumenes) or contain multiple cells, comprised of multiple cells adjoining one another.

Video 1 caption: A female works the wet mud bolus with her mandibles to add an additional layer of mud to the edge of a partially completed cell.

For those mason or potter wasp species that construct free-form mud nests, a significant amount of time and energy is allocated toward water and soil collection to make mud. Mud is used to make one or multiple cells/enclosures that house a number of caterpillars, and eventually the developing wasp larva. To make mud, the wasp female first finds a water source, imbibes the water storing it in her crop, then searches for the perfect soil type to begin collecting soil particles. Each mason wasp can have their own unique soil preferences, some preferring sand, while others may seek out sandy loam soil. Perching on the ground, she scrapes and gathers a ball of soil particles in her mandibles and simultaneously regurgitates some water to form a mud bolus. When the bolus is sufficiently moistened and large enough, she carries it back to the nest held in her mandibles.

A female spends the night in a newly formed mud cylinder/cell. She’ll complete construction and provisioning of the cell the following day.

This month in my garden, I found a Walden's mason wasp female (Ancistrocerus waldenii) constructing a free-form mud nest on the side of a rock. This wasp species prefers to construct its nest attached to a hard surface such as a rock, concrete, or even on the side of a terra cotta flower pot! The rock in my garden that she selected has multiple concave indentations; these convenient divots helped form the back wall of the mud cells. After selecting the nest site, nest initiation begins with the construction of a single mud cylinder, and each layer of mud that forms the cylinder requires several mud-collection foraging trips. Once the cylinder-shaped cell is large enough to hold several moth caterpillars, the wasp female lays a single egg, suspended from the roof of the cell by a silken thread. Many solitary wasps lay their egg on one of the prey cached in the cell after they have fully provisioned the cell; eumenids, however, typically lay their egg in an empty cell prior to provisioning the cell with prey.

A closeup of an Ancistrocerus waldenii female peering out of an incomplete mud cylinder. This unfinished cell provides a convenient enclosure for her to spend the night, rest, or avoid inclement weather.

Providing food for her future developing larva comes next. She hunts for moth caterpillars on plant foliage, captures one, stings it to cause paralysis, then carries the caterpillar clutched beneath her. She fills the cylinder with multiple immobilized caterpillars, an average of nine, seals off the end of the cylindrical cell with mud, then begins the construction of the next, adjoining mud cylinder. Her egg, safely suspended from the roof of the cell, will hatch in the next few days and the tiny, first instar larva will drop onto the cache of caterpillars and begin feeding. The venom that paralyzed the caterpillars also keeps them alive for several days, long enough for the developing wasp to have a fresh and live supply of food while it develops.

An Ancistrocerus waldenii female returns to her nest with a bolus of mud held clasped in her mandibles. She is adding an additional layer of mud over multiple fully provisioned cells.

An Ancistrocerus waldenii nest can have multiple mud cylinders/cells, constructed adjoining or on top of one another. After all of the cylinders are complete and provisioned with prey, the female adds an additional thick layer of mud over the entire nest to help seal it off from predators and help prevent the nest from breaking down before the wasps inside emerge as adults.

Here are a few tips for identifying Ancistrocerus waldenii females although if you find a similarly-constructed mud nest attached to a hard surface, that will help narrow down your identification to a few species. Wasps in the genus Ancistrocerus have a prominent transverse carina [ridge] on the base of their first abdominal segment (T1, for tergum one, the first visible dorsal plate). Ancistrocerus waldenii has white (less often yellow) markings. The female has a spot on the top of the sixth abdominal segment (T6) and complete apical bands on the first through fifth abdominal segments (T1 to T5). The female also has entirely black antennae (many mason wasps have yellow or white markings on the underside their antennal scape [first long segment of the antenna, nearest face]).

Be sure to visit Pollination Press, LLC, Heather's publisher, and shop for her books. Her book on wasps is a fine complement to my own; and who doesn't need another guide to native bees? Thank you, Heather, for agreeing to do this guest post.

Wasp Wednesday: Southern Yellowjacket

Upon returning home last Thursday, I noticed the silhouette of what I thought was a paper wasp on the inside of one of the garage windows. It turned out to be something more exciting than that. Here in eastern Kansas, it is the time when female social wasps of all sorts are founding new colonies, or at least seeking a place to set up housekeeping. This individual is no exception, but she also has a devious alternative strategy she can use.

I gently captured the wasp in a plastic vial. In better light she was instantly recognizable as a queen of the Southern Yellowjacket, Vespula squamosa. This species is not quite as common as other species in eastern North America, so it was nice to have a chance to see one up close and finally get some respectable images of those muted ochre and yellow colors. As beautiful as these wasps are, their biology is even more fascinating and somewhat frightening.

Southern Yellowjacket is sometimes an "inquiline," a facultative social parasite of other yellowjacket species, namely the Eastern Yellowjacket, Vespula maculifrons, but also the Widow Yellowjacket, Vespula vidua. That is to say that while Southern Yellowjacket can exist like any normal, free-living yellowjacket species with a queen, worker caste, and males and new queens at the end of the colony life cycle, it can also hijack the colony of another species for its own benefit of free labor. Conversely, an obligate social parasite cannot exist on its own. It must successfully usurp a host nest. Obligate social parasites have no worker caste, only queens and males (in the case of yellowjackets).

Southern Yellowjacket worker from Ohio, USA

Competition for optimal, concealed nesting sites can be keen, so social parasitism may have evolved as one way to solve this problem. Eastern Yellowjackets typically nest in abandoned rodent burrows and similar cavities, but they can also nest in wall voids of human structures. It is telling that colonies of this species in disturbed habitats and urban and suburban locations appear to be the most vulnerable to being taken over by Southern Yellowjacket.

The Southern queen typically invades an embryonic nest of its host, dominating, evicting, or killing the resident queen. There may or may not be any host workers at the outset, but eventually the nest is converted entirely to Southern Yellowjacket workers. Evidence of the host remains in the differing architecture of the nest. Southern Yellowjacket is a significantly larger insect than Eastern Yellowjacket, so the cells in the paper combs of the nest differ accordingly.

Southern Yellowjacket male from Tennessee, USA

A mature nest of Southern Yellowjacket, persisting into late autumn, may contain an average of 5,000 cells. That is a lot of wasps! Southern Yellowjacket is not inherently more aggressive than most other yellowjacket species in defense of their nest, but more workers means a greater response to disturbance. You may want to inspect your yard carefully before using any powered tools that could cause vibrations and spark a yellowjacket offensive.

Southern Yellowjacket ranges from the Great Lakes to the Atlantic coast south of New England, to Florida, and west to Iowa, Kansas, and most of eastern Texas. It also occurs in southern Mexico and Guatemala, making it quite literally our southernmost species of yellowjacket.

Sources: Akre, R.D., A. Greene, J.F. MacDonald, P.J. Landolt, and H.G. Davis. 1980. Yellowjackets of America North of Mexico. U.S. Department of Agriculture, Agricultural Handbook No. 552, 102 pp.
Kratzer, Chris Alice. 2022. The Social Wasps of North America. Frenchtown, New Jersey: Owlfly Publishing, LLC. 417 pp.

The Wasp Wall

South Cape May Meadows in Cape May, New Jersey is a property managed by The Nature Conservancy (TNC) for birds and other wildlife. Near the parking lot stands a shed that itself is something of a refuge for a whole community of insects. One wall, facing west and with beams that make something of an overhang or trellis, is being worked over by the Eastern Carpenter Bee, Xylocopa virginica. The abandoned nests of these solitary bees are then used by mason wasps, leafcutter bees, and other solitary Hymenoptera.

The shed at South Cape May Meadows, behind the arbor entrance

During our visit this past September 24, we noticed the holes, then soon saw females of the Four-toothed Mason Wasp, Monobia quadridens, exploring some of those cavities. I wrote about this species previously, detailing its life cycle, but this was the first time I had observed them coming and going from nests.

Female Monobia quadridens entering her nest

One female delivered a paralyzed caterpillar during our observations. It was a surprisingly small larva given the size of the wasp, but then she caches several victims in each cell before laying a single egg, putting up a partition of mud, and then starting a new cell along the length of the tunnel inside the wood.

Female cuckoo wasp, Chrysis sp., prospecting for a host

One might think that nests in such solid material would be impermeable to parasites, but not so. We watched a brilliant blue-green cuckoo wasp, Chrysis sp., investigate some of the holes for occupants. Given a nest in progress, she would infiltrate and lay her own egg inside. Her larva would then consume the prey items left by the rightful owner for its offspring. Cuckoo wasps are nearly impregnable, with a very dense exoskeleton that deflects the bites and stings of host wasps. Cuckoo wasps can roll into a ball to further protect themselves.

Female Leucospis affinis ovipositing in a host nest

A less common parasitic wasp also came to the wall. Leucospis affinis is a large chalcidoid wasp. The female is easily recognized by the whip-like ovipositor that curls over the top of her abdomen. The ovipositor is the organ she uses to lay her eggs....by drilling through the solid wood directly into one of the cells of her host. How she divines the location of a host larva through a layer of dense cellulose is a mystery to me, but her aim is usually true.

Nest closure of mason wasp or carpenter bee

A completed nest of a mason wasp is usually identified by the mud plug that closes the entrance to the hole in the wall. Because the soil at Cape May is essentially all sand, it was difficult to tell if we were looking at a sand closure or a sawdust closure that would be the work of one of the carpenter bees.

Nest closure of leafcutter bee, Megachile sp.

Easier to identify was the completed nest of a leafcutter bee, genus Megachile. Leafcutter bees snip oval pieces from leaves of living plants and fashion those clippings into barrel-shaped cells that they stack along the length of a tunnel in wood, or underground in the case of a few species. The female bee then cuts at least one perfectly circular leaf fragment that serves as a "lid" for the completed cell.

Nest of grass-carrier wasp, Isodontia sp.

We found one hole filled loosely with bits of grass, and we surmise this was the work of yet another kind of wasp, the grass-carrier. These solitary wasps, related to mud daubers in the family Sphecidae, use dry grass to fill, and/or partition, and plug their nest tunnels. Near Cape May Point State Park we did witness a female Isodontia mexicana select and bite off a dry grass stem to take back to her nest, so we know these insects were active.

Female grass-carrier wasp, Isodontia mexicana, cutting a piece of grass

Ironically, one other kind of wasp was tearing the wall down one mouthful at a time. Workers of the Bald-faced Hornet, Dolichovespula maculata, would alight on the wall and begin chewing off wood fibers to mix with their own saliva. This creates a pulp that they use to make durable paper nests. Looking more closely at the wall we realized that the scores of yellow streaks on the otherwise weathered gray wooden surface were where yellowjackets (of which the Bald-faced "Hornet" is just another species) had stripped fibers for use in building their nests.

Bald-faced Hornet gathering wood fibers to make paper

No doubt, earlier in the season there would be even more activity around this wall. The shed is still standing, sturdy as ever, so the insects are not doing much, if any, structural damage. Please consider that if you find that your own shed is becoming home to carpenter bees and other insects. You may find yourself as enthralled as we were by the little ecosystem started by carpenter bees.

Female Monobia quadridens exiting her nest

Sources: Evans, Howard E. 1963. Wasp Farm. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 178 pp.
Buck, Matthias, Stephen A. Marshall, and David K.B. Cheung. 2008. “Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region,” Canadian Journal of Arthropod Identification No. 5: 492 pp. (PDF version).
Krombein, Karl V. 1967. Trap-nesting Wasps and Bees: Life Histories, Nests, and Associates. Washington, DC: Smithsonian Press. 570 pp.
Krombein, Karl V., et al. 1979. Catalog of Hymenoptera in America North of Mexico Vol.2 Apocrita (Aculeata). Washington, DC: Smithsonian Institution Press. Pp. 1199-2209.

The Wasps and the Fly

You literally don't have to do anything but step out the door to observe fascinating phenomena in the world of insects. I did just that on August 9th, and found myself watching peculiar behavior between a nest of European Paper Wasps, Polistes dominula, and an unidentified fly.

The paper wasp nest has been on the back of our fence gate for months, now. The occupants are amazingly tolerant, even as we come and go. They may get a bit disoriented if we leave the gate open for a lengthy period, but otherwise they are innocuous and we let them be. Imagine my surprise when the thing that has agitated them most was what appeared to be a house fly.

Upon closer examination, the fly had slightly different markings than a house fly, was spinier on the abdomen, and had perhaps longer legs. It walked a lot, nervously, and it was difficult to even get an image of it. Finally, it stopped walking and started, well, stalking towards the wasp nest. One wasp took notice and adopted a very alert posture. Suddenly, the fly flew off its perch and looped around the wasp nest at dizzying speed. It was so quick I was not sure what I was seeing.

The aftermath of the fly's reconnaissance mission was even more dramatic. The one wasp that had seen the fly in the first place suddenly began running frantically and erratically all over the comb, for probably at least ninety seconds. The fly was long gone, but I was suspecting that maybe it had laid an egg and that was the object of the wasp's energetic searching behavior.

Still puzzled by the fly's identity, I took to the internet for the most likely suspects: a tachinid fly, family Tachinidae; or a parasitic sarcophagid (Sarcophagidae). I found a tachinid that looked promising, but viewing images of the species it became readily apparent this was not the right one. Sarcophagids came up empty as well. Furthermore, I have witnessed paper wasps eating sarcophagids, not falling victim to them. Next I looked to my library and found a potential match in a European field guide, of all things. Eustalomyia festiva, a member of the diverse but obscure family Anthomyiidae, looked good. According to the text, it "Breeds in [the] bodies of flies stored by solitary wasps." Ok, but paper wasps are social....

I posted the images shown here on the help group "Hymenopterists Forum" on Facebook, and got this reply from Rui Andrade:

"It looks like Eustalomyia (Anthomyiidae). The larvae are kleptoparasites of wasps."

This makes sense to a degree, but social wasps do not store their prey for later consumption by their larval offspring. They feed masticated prey directly to the larvae. There is therefore no opportunity for a fly larva to develop in a social wasp nest under those circumstances, as a kleptoparasite feeding on prey intended for the host's offspring. The only alternative I can fathom is that the fly is parasitic on the wasp larvae themselves. Cursory review of the literature does not inform my opinion, as they all stubbornly state that solitary wasps are the victims of Eustalomyia. The wasps are not going to let me peer into each cell to see if there is something other than a wasp egg or larva inside, either.

Perhaps this one individual fly was just confused as to the proper host. Maybe it was initially attracted to the bee block ("bee condo") hanging up on another part of the fence, where we have indeed had solitary wasps nesting. This year the bee condo has been devoid of activity for the most part, so maybe scaring the paper wasps was an amusement borne of frustration for this fly. We may never know.

Sources: Chinery, Michael. 2012. Insects of Britain and Western Europe. A Domino Guide. London: Bloomsbury Publishing. 320 pp.
McGavin, George C. 1992. The Pocket Guide to Insects of the Northern Hemisphere. London: Parkgate Books, Ltd. 208 pp.

More Drama at the Bee Block

I was going to write at some point about how one of the other benefits of putting up a bee block ("bee condo") for solitary bees and wasps is that their parasites have a harder time finding them there than in a more natural situation. Well, last week I was proven completely wrong about that. On the positive side, I identified two new tenants in the block in our backyard.

Female mason bee, Heriades sp., on milkweed, before I had identified it

Early in the week I happened to see an insect fly from one of our blooming milkweed plants and literally make a bee line into one of the smaller holes in our bee block. I was not able to make an identification, so swiftly did it disappear.

Stakeout: female Sapygid wasp patiently eyeing potential hosts

Friday, June 24, I happened to glance at the bee block and noticed a very slender insect in one of the corners. I broke out the camera, took a couple pictures, and identified it as a sapygid wasp, family Sapygidae. Sapygids are parasitic on bees in the families Megachilidae and Apidae, and mason wasps in the family Vespidae, subfamily Eumeninae. The larvae of the sapygids either feed on the food stored for the host's offspring, or live as ectoparasites on the host larvae. Great.

Territorial dispute? Another sapygid joins the first one

Oh, here comes *another* sapygid. There were two on the nest block for only a brief time, and though it is not easy to separate the genders, I had no way of telling if it was a pair, or I believe they were two competing females. Males have even longer antennae and a blunter tip to the abdomen.

While photographing one of the sapygids, I got lucky. One of my pictures captured the mystery lodger in the bee block from earlier in the week.

Target detected: Sapygid wasp spies Heriades mason bee giving away its nest location

The insect coming to one of the smallest diameter holes is a type of mason bee in the genus Heriades. There are only eleven species of Heriades in North America north of Mexico, and five species in Colorado. Only Heriades cressoni has been officially recorded in El Paso County, but our bee block resident could still be one of the other species.

The female bee uses a pre-existing tunnel, such as an old beetle boring in a dead tree or log, or a hollow twig, in which to make her nest. She creates a series of cells with a partition of plant resin dividing one from another. She usually leaves one empty cell at the entrance before sealing the completed nest with a resin plug. Should a parasite break in, it might be duped into thinking the nest was empty; or at least dissuaded from having to break through a second "door."

Female Heriades sp. mason bee collecting pollen beneath her abdomen

The mother bee gathers pollen with a brush of hairs on the underside of her abdomen. Back at the nest she mixes the pollen with nectar she regurgitates from her crop (an internal food storage organ). This is "bee bread" that she fashions into a ball or "loaf" for each cell. She then lays an egg in the cell, and finally seals it with the resin partition. She repeats this scenario until the nest cavity is filled.

The sapygid wasp that had been waiting patiently for just the right moment to lay her own eggs in the bee nest finally made her move. She quickly backed halfway into the hole on the bee block and presumably deposited one or more eggs before fleeing the scene. This is the strategy that many, if not most, bee parasites use. They stake out a nest in the process of being provisioned, and enter when the host bee leaves to gather more nectar and pollen, or material used in making a partition between cells.

Game on! Female sapygid wasp laying eggs in Heriades mason bee nest

Another surprise happened when I saw a mason wasp approach and then enter another hole on the block. This one is different from the one I wrote about a couple weeks ago. It is smaller and more ornately patterned. It is either Parancistrocerus sp. or Stenodynerus sp. One cannot tell the two apart from images of live specimens in most cases. Even with actual specimens under a microscope it is difficult to make an identification. Like most cavity-nesting mason wasps, paralyzed caterpillars will serve as food for the larval offspring.

Female mason wasp, Parancistrocerus sp. or Stenodynerus sp.

I can hardly wait to see what comes next to our bee apartment building. Please comment if you yourself have a bee block (or more than one), and share what is coming and going from it, what parasites or predators you have seen lurking, and any other pertinent observations.

Sources: Krombein, Karl V. 1967. Trap-nesting Wasps and Bees: Life Histories, Nests, and Associates. Washington, DC: Smithsonian Press. 570 pp.
Scott, Virginia L., John S. Ascher, Terry Griswold, and César R. Nufio. 2011. "The Bees of Colorado (Hymenoptera: Apoidea: Anthophila)," Natural History Inventory of Colorado No. 23, University of Colorado Museum of Natural History, Boulder, Colorado. 112 pp.
Scott, Virginia. 2015. "Resin Plugs (part 1) and Their Bugs," The Bees' Needs Blog.

The Mason Wasp Euodynerus foraminatus Endorses Bee Blocks

Those "bee blocks," chunks of wood with holes of varying diameters drilled into them, are all the rage now for attracting solitary native bees like leafcutter bees and mason bees. They do work, no matter where you live, and I have proof. Ok, so the first occupant in our newly-hung bee block is actually a wasp, but that is also a good thing, and I'll explain why.

A bee block need not be as fancy as the one shown here. There are some standards you should adhere to, though, and a thorough explanation is found here. Solitary bees come in a variety of sizes, so having a good selection of various diameter holes is helpful.

Why am I excited that a solitary wasp is using our block? Wasps are "flower visitors" that go to flowers strictly for nectar to fuel their activities (think gas station, not grocery store), but they do a fair bit of pollinating in the process. The biggest benefit of wasps, though, is that they are parasitoids of insects we consider pests.

The scenario for the mason wasp using our nest box, Euodynerus foraminatus, goes like this: The female wasp catches and paralyzes a caterpillar, and flies it back to the nest hole where she stashes the victim, and usually several more, as a larder of food for a single larva offspring. She lays an egg on the first or last victim, and then erects a mud partition. She repeats the steps, such that one of those holes you drilled might end up filled with several cells, each holding numerous caterpillars that won't be eating your garden plants. The preferred prey of E. foraminatus are larvae of moths in the families Oecophoridae, Tortricidae, Gelechiidae, Pyralidae, Crambidae (subfamily Pyraustinae). All of these include some notorious pests, as well as caterpillars that conceal themselves in rolled or tied leaves that other wasps won't go to the trouble of extracting.

We know at least one nest tunnel is complete because it has been plugged with mud. You can identify the different types of bees and wasps using a "bee condo" by the kinds of closures they make. Some megachilids (mason and leafcutter bees) will make the final closure with a plug of chewed-up leaves. Other bees will plug a nest hole with plant resins.

Besides the comings and goings of the bee block inhabitants, you can get some other kinds of drama. While watching the bee block for signs of activity last Friday, I noticed a crab spider hanging out under the "eave" on our bee block. Sure enough, when the wasp approached the spider reacted, hanging of the roof and opening its "arms" in a potentially lethal embrace. The wasp ignored or never noticed the threat, but I ushered the spider to another part of our yard anyway.

You may think that there is no way one of these boxes would work in your yard. The above image is of our yard, behind our townhouse unit. Look at it! It is literally like ten-by-twelve feet. Surely, if we can make this work, so can you. It takes virtually nothing to put one up, and it offers both critical bee real estate for the insects, and hours of entertainment for you and your family. Since solitary bees and wasps do not have vast quantities of offspring and honey stores to defend, they are not going to sting you. Besides, they are too busy working.

Back to that mason wasp for a second. Euodynerus foraminatus is a very widespread species, found coast to coast in the United States, plus all Canadian provinces, and down into Mexico, too. There is a very good chance you could attract one to your own bee block.

Sources

: Buck, M., Marshall, S.A. and Cheung D.K.B. 2008. "Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region," Canadian Journal of Arthropod Identification No. 5: 492 pp. (PDF version).
Stone, H.B. 2014. "Insects of the Week: Eumenids and Chrysidids," The Bees' Needs Blog.

Makin' Paper

This has been an exceptional year for paper-making social wasps in the family Vespidae here along the Colorado Front Range. Most species of paper wasps and yellowjackets have been unusually abundant, much to the consternation of the average person who despises any stinging insect. However, there is much to admire about these industrious organisms, not the least of which is the amazing architecture of their nests.

Western Paper Wasp nest (Mischocyttarus flavitarsis)

Nests of most social vespids are made of repurposed or recycled cellulose from dead, woody plants and trees. The wasps manufacture the paper by scraping fibers and chewing them into a ball of pulp that is taken back to the nest and applied as a thin strip that soon dries into a surprisingly durable, stiff material.

Bald-faced Hornet worker scraping wood fibers

Paper wasps in the genera Polistes and Mischocyttarus here in Colorado make exposed paper combs that are frequently suspended under the eaves of buildings. Yellowjackets, including the Bald-faced "Hornet," Dolichovespula maculata, house their combs within a layered paper envelope. Species in the genus Dolichovespula build their nests above ground, usually in a tree, shrub, or among berry canes. Species in the genus Vespula normally build their nests underground in abandoned rodent burrows and other pre-existing cavities that they can expand by excavating around the nest.

Huge European Paper Wasp nest

I was surprised to find out that paper wasps will re-use old nests! One particularly impressive nest of European Paper Wasps (Polistes dominula) is situated under an overhang at my workplace in Colorado Springs. It appeared abandoned when I first started work there, but was quickly occupied and even expanded later in the season. This is an impressively large nest that would probably not fit on a dinner plate, very unusual for any species of Polistes.

Active nest of Bald-faced Hornets

I also discovered an active nest of the Bald-faced Hornet in North Cheyenne Cañon on August 21. Fortunately, it was far enough off the trail to not be a potential hazard to the many people that use the park; and far enough off the trail to make it difficult for anyone to destroy the nest. I went back a month later (September 18) and found the wasps had expanded the nest and changed its shape from oval to a roughly football shape. There was no evidence of activity, and indeed the colony cycle for this species is shorter than that of other social wasps.

Bald-faced Hornet nest on August 21

The same nest on September 18

Underground nests like that of the Western Yellowjacket (Vespula pensylvanica) and Prairie Yellowjacket (V. atropilosa) are more problematic because one can easily disturb an unseen nest with painful results. I only notice nests when my eye catches a steady stream of yellowjackets coming and going from a common point.

Western Yellowjacket nest entrance. Note exiting workers carrying soil pellets

Paper wasps are generally welcome predators of caterpillars and other soft-bodied insect pests. The Bald-faced Hornet is a predator of flies that is never a pest at picnics and barbecues. The same is true of the Prairie Yellowjacket. Meanwhile, the Western Yellowjacket is a scavenger that will take your lunch away from you given the opportunity. Gently waving your hand can eventually discourage the wasp's efforts.

Prairie Yellowjacket worker eating insect

We may have these wasps to thank for inspiring the invention of the paper that we use today. At least some accounts trace observations of wasps in ancient China to the origins of human papermaking.

How to (Almost) Catch a Leaf-tier Caterpillar (Video)

Last week I wrote about a mason wasp that successfully captured a leaf-rolling caterpillar. Amazingly, the day after I made that observation, I saw another species of mason wasp hunting a slightly different kind of caterpillar. This time it was a female Ancistrocerus campestris attempting of fish out a leaf-tier caterpillar (genus Psilocorsis, family Amphisbatidae) from its shelter between two lashed-together oak leaves.

The drama unfolded at Tully Lake, between Athol and Royalston in north-central Massachusetts, by the boat launch. I happened to notice the same schizophrenic behavior in this wasp that I had observed in the female Ancistrocerus unifasciatus female the previous day. I turned on the video feature of my camera a number of times, for long durations, but this wasp's attempts were ultimately unsuccessful.

Leaf-tiers, in contrast to leaf rollers, can involve more than one leaf, creating a "sandwich" like the one the wasp is exploring in the images and video here. I concluded, given the host plant (oak), that this was likely the work of a caterpillar in the genus Psilocorsis in the family Amphisbatidae. That information also helped me in my assessment of the wasp's identity.

Ancistrocerus campestris is of average size for a mason wasp. The forewing length of females ranges from 9-11 millimeters, and 6.5-9 mm for males. The color pattern on the abdomen is fairly consistent, the hind margins of the first three abdominal segments colored in yellow. The genus Ancistrocerus can be identified by a transverse ridge along the front surface of the first abdominal segment, creating an abrupt angle and "face" that faces the rear of the thorax. In other genera the abdomen slopes more gently toward the thorax.

This time, the wasp did try to tear into the leaf shelter, evidenced by the holes she chewed in the surface of the top leaf. The brown patch is likely the result of the caterpillar feeding on the bottom surface of that top leaf. The wasp also ran around the entire edge of the shelter, trying to wiggle inside and grab the occupant.

Had she succeeded, she would have flown her prize to her nest, inside a pre-existing beetle boring in wood, a hollowed-out sumac twig, or an abandoned mud dauber nest. She divides such tunnels into cells, after completing a single cell by laying an egg and then caching several paralyzed caterpillars. She uses mud to make partitions between cells, and for the plug that closes a finished nest. A nest may contain anywhere between two and eleven individual cells. This wasp has, on one occasion, been seen taking over active nests of the keyhole wasp Trypoxylon clarkei, kicking out the rightful owner.

Besides caterpillars in the family Amphisbatidae, this mason wasp uses caterpillars from the family Gelechiidae ("twirler moths").

Nests can be invaded by parasites including the bee fly Toxophora amphitea, and the tiny eulophid wasp Melittobia chalybii. Grubs of the wedge-shaped beetle Macrosiagon cruentum may prey on the wasp larvae.

Ancistrocerus campestris can be found from southern Ontario, Canada through New England south to Florida, and west to Minnesota, South Dakota, Kansas, and Texas. Look for this species along forest edges in woodland habitats.

Sources: Buck, M., Marshall, S.A. and Cheung D.K.B. 2008. "Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region," Canadian Journal of Arthropod Identification No. 5: 492 pp. (PDF version).
Eiseman, Charley and Noah Charney. 2010. Tracks & Signs of Insects and Other Invertebrates. Mechanicsburg, Pennslvania: Stockpole Books. 582 pp.
Krombein, Karl V., Paul D. Hurd, Jr., David R. Smith, and B.D. Burks. 1979. Catalog of Hymenoptera in America North of Mexico Volume 2. Washington, DC: Smithsonian Institution Press. pp. 1199-2209.
Krombein, Karl V. 1967. Trap-nesting Wasps and Bees: Life Histories, Nests, and Associates. Washington, DC: Smithsonian Press. 570 pp.