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.

Pipe Organ Mud Dauber, Trypoxylon politum, Found in Colorado

Yet another insect species appears to be expanding its range into eastern Colorado. I have recently discovered nests of the Pipe Organ Mud Dauber, Trypoxylon politum, at three locations in the vicinity of Colorado Springs.

This species is common throughout the eastern United States, but was previously known only as far west as Kansas and Nebraska. It is named for the multiple tubular mud columns that comprise its nest, and resemble the pipes on old-fashioned organs.

The nest from Fountain Creek Regional Park

Trypoxylon politum is not related to the familiar Black and Yellow Mud Dauber, or the Blue Mud Dauber, both of which are in the family Sphecidae. The Pipe Organ Mud Dauber is a member of the family Crabronidae, collectively known as "square-headed wasps." This is our only North American member of the "fabricator species group" of Trypoxylon that create free-standing mud nests. Most Trypoxylon species nest in pre-existing cavities such as nail holes, beetle borings in wood, and hollow stems or twigs.

Female working on the Bear Creek Nature Center nest

The first evidence I found of this species in Colorado was a pair of nests in the rafters of a large outdoor picnic shelter (ramada) in Bear Creek Regional Park near the foothills of the Front Range in Colorado Springs. That was on July 21, 2015, and I thought it might be a fluke. Maybe one wasp hitched a ride in a nest adhered to an object transported from an eastern state. That is still a likely scenario, but....

My wife then discovered a second nest on the inside wall of a wildlife viewing shelter in Fountain Creek Regional Park, on August 3. The park is located between the towns of Security/Widefield and Fountain, in El Paso County south of Colorado Springs. The longest column in this nest measured at least five inches. You cannot say these wasps lack ambition. One female created this entire nest.

The nest from Bear Creek Nature Center, August 13

Most recently I discovered a single-column nest on the exterior of the Bear Creek Nature Center, also located in Bear Creek Regional Park, Colorado Springs. That was yesterday, August 13. Well, it was a single-column nest. This morning, August 14, I discovered the female wasp completing a second tube. I managed to get a few grainy images and a couple nice videos, which I am sharing here.

Female bringing mud ball for second column in the Bear Creek Nature Center nest

A bit of architectural information. Each tube is partitioned on the inside into several individual "rooms," constructed individually from back to front inside the tube. The female wasp hunts spiders, especially orbweavers, paralyzing them and caching several per cell, laying an egg on the last victim before creating a mud partition and beginning the process again. She continues this until the column is filled.

The column itself resembles braided hair. One ball of mud, carried by the wasp up to the nest, is rolled into a thin half-arc. The next load is used to create the opposing, complimentary half-arc. Watch it happen in this video.

The female wasp works with astonishing speed. She could fly away and return to the nest with another ball of mud in about sixty seconds.

Sometimes, females work in tandem with a male. The male has a spine resembling a fishhook on the underside of the first abdominal segment. It helps anchor him in the nest when he is fending off enemies like parasitic wasps, flies, and other males of his species. The wasp here seemed to be working alone.

It will be interesting to see how well the Pipe Organ Mud Dauber succeeds here when we already have three species of mud daubers (including the new invasive species Sceliphron curvatum). They all coexist elsewhere, so maybe it will be the spiders that will suffer the most.

Masters of Mud: Auplopus Spider Wasps

The first image in this post is not of the insect I will be discussing today. That is because I am far more frequently asked what these little mud barrels are, and what makes them. Indeed, you are more apt to stumble upon these nests than you are to see their maker. While most spider wasps in the family Pompilidae dig burrows for their nests, or exploit pre-existing cavities, those in the genus Auplopus create free-standing mud cells.

I have few images of these wasps, and detest “stealing” images from others for my posts even though I give full credit when I do, so I hadn’t done an entry about Auplopus until now. It took a Facebook post by Eileen Miller to remind me that I was overdue to address them. Eileen was kind enough to share her own images in exchange for learning more about the wasps and their nests.

© Eileen Miller

There are ten recognized species of Auplopus in North America, but the genus is in dire need of revision. Collectively, the genus occurs across the entire continent. One species, A. carbonarius, is introduced from western Europe, and has been documented in New York and Michigan, but probably has a wider distribution in the U.S. than is currently known.

Several species are bright metallic blue-green, and the females at least are basically inseparable externally. Males can be identified by differences in the genitalia. Auplopus are small, averaging about 10 millimeters in length. Females have an oval spot on top of the abdomen near the tip called a “pygidial plate” that they use like a masonry trowel to manipulate mud pellets into segments of their mud nests. The female curls her abdomen beneath her during such work, so that the pygidial plate can contact the mud.

© Yurika Alexander via Bugguide.net Auplopus mellipes female

The nests are usually constructed inside pre-existing cavities in wood, or at least in sheltered niches such as under bark on standing trees, crevices in rock walls, or even inside the abandoned nests of other wasps like Sceliphron caementarium (Black and Yellow Mud Dauber), Trypoxylon politum (the Pipe Organ Mud Dauber), and paper wasps (Polistes spp.). The tiny barrel-shaped cells are roughly 15 millimeters in length and 7-10 millimeters wide, often stacked end-to-end, two to five per row.

Nest inside hole where a bolt used to be

The wasps appear to be mostly opportunistic hunters of spiders that do not spin webs.

Documented prey includes spiders from thirteen different families: Crab spiders (Thomisidae), jumping spiders (Salticidae), sac spiders (Clubionidae), ground sac spiders (Trachelas sp. in Corinnidae), ghost spiders (Anyphaenidae), longlegged sac spiders (Cheiracanthium sp. in Miturgidae), ground spiders (Gnaphosidae), nursery web spiders (Pisauridae) being the usual victims of North American Auplopus.

© Marie L. Schmidt via Bugguide.net Female wasp with spider prey

Adult or immature spiders may be taken, and the wasps usually amputate several, if not all, the legs of their prey. This allows the wasp to feed on the blood of the spider, but also facilitates easier transport of the victim over the ground. Presumably, more than one spider is placed in each mud cell before the female lays an egg on the last victim and then seals the cell.

© Eileen Miller, inside of cell showing pupa in cocoon

In at least one species, the emerging adult wasp regurgitates liquid to soften the mud cap on its cell, allowing it to more easily chew its way to freedom.

Auplopus seldom visit flowers, but can often be found around aphid colonies on honeyvine milkweed (Ampelamus albidus, Cynanchum leave), sunflower, and other plants. They feed on “honeydew,” the sweet liquid waste products that aphids secrete.

© Eileen Miller

Look for these little wasps from May to October, but especially July through September when they are most abundant. It should be noted that other Hymenoptera make very similar mud nests, particularly some of the Osmia mason bees, and some mason wasps (family Vespidae, subfamily Eumeninae). Auplopus are surprisingly well-studied insects, but information is scattered over articles in many different scientific journals and books.

Sources: Eiseman, Charley and Noah Charney. 2010. Tracks & Signs of Insects and Other Invertebrates. Mechanicsburg, Pennsylvania: Stackpole Books. 582 pp.
Evans, Howard E. and Carl M. Yoshimoto. 1962. “The Ecology and Nesting Behavior of the Pompilidae (Hymenoptera) of the Northeastern United States,” Misc. Publ. Entomol. Soc. Am. 3(3): 66-119.
Krombein, Karl V. 1967. Trap-nesting Wasps and Bees: Life Histories, Nests, and Associates. Washington, DC: Smithsonian Press (Publication 4670). 570 pp.
Kurczewski, Frank E. 1989. “Observations on the Nesting Behavior of Auplopus caerulescens subcorticalis and Other Auplopodini (Hymenoptera: Pompilidae),” Gt. Lakes Entomol. 22(2): 71-74.
Kurczewski, Frank E. and Mark F. O’Brien. 1991. “Auplopus carbonarius, a Palearctic Spider Wasp, Extends its Range to Michigan (Hymenoptera: Pompilidae),” Gt. Lakes Entomol. 24(3): 185-186.
O/Neill, Kevin M. 2001. Solitary Wasps: Behavior and Natural History. Ithaca, New York: Comstock Publishing Associates (Cornell University Press). 406 pp.

Wasp Wednesday: Black & Yellow Mud Dauber

Few wasps in North America are as ubiquitous and conspicuous as the familiar Black and Yellow Mud Dauber, Sceliphron caementarium. Even when the wasps themselves are not obvious, their mud nests are often are. Homeowners consider the amorphous clod-like nests to be eyesores, if not a hazard when the female wasp is at work on one. Take a closer look, and you will be amazed by the wasp and her legacy of insect lodging.

Sceliphron caementarium has an extraordinarily widespread geographic distribution, and varies markedly in its appearance from north to south. Northern specimens tend to be mostly black, with dark, violaceous wings. Western specimens tend to be more yellow, with yellow wings.

Not only does this species occur from Canada to Central America and Peru, it has been introduced to the West Indies, Bermuda, Hawaii, the Marshall Islands, Cook Islands, Society Islands, New Caledonia, Australia, Fiji, Samoa, France, and Germany. Once again, international commerce has played a role in the wasp’s seemingly jet-setting lifestyle. Females may build nests inside of shipping containers that then make landfall at various ports.

Why does the Black and Yellow Mud Dauber succeed wherever it finds itself? The female wasps are generalist hunters of spiders, and spiders can be found everywhere as well. The wasp first finds a place to build her nest, usually in a sheltered situation such as beneath a rock overhang. Once she establishes a suitable location, she flies off to a patch of mud and rolls up a ball with her jaws and front legs. She then flies off with this pea-sized load and plasters it to the construction site she chose earlier.

Once she has laid down a layer of mud on the surface of the substrate, she begins fashioning a three-dimensional cell. Each subsequent load of mud makes a “rib” that reaches across half the span of the cell she is building. The arcs from either side meet at the middle, dovetailing nicely with each other and the adjacent ribs on the same side. Once the cell is completed, leaving an opening at one end, she may plaster more mud over the ribs, obliterating the initial artistic appearance of the cell.

A finished cell is then provisioned with paralyzed spiders captured by the wasp. She uses her sting to subdue her prey, but does not kill it. A comatose spider won’t spoil before her larval offspring has a chance to feed on it. Many spiders are harvested and packed into the cell. The wasp usually lays an egg on the first spider to go into the cell. Orb weavers and crab spiders seem to make up the bulk of prey, but the wasps are opportunists and will not hesitate to take other kinds of spiders.

Most female mud daubers make more than one cell, the next one placed immediately beside the previous one. The whole series of cells may then be covered in mud, making it look like some mischievous teenager hurled a clod onto a wall. Not very pretty, but an effective fortress against parasites.

And do mud daubers ever have parasites! Chief among them are the cuckoo wasps of the family Chrysididae. These little metallic jewels wait for the hard-working mud dauber to go off on the hunt again, then enter the nest and lay an egg inside. Should the mud dauber catch the intruder, the cuckoo wasp roles into a tight ball, its dense cuticle impervious to the stings and bites of its irate host. Chrysis angolensis is an African species now well-established in North America, but there are native species that attack the mud dauber, too.

Other enemies of the Black and Yellow Mud Dauber include ichneumon wasps in the genera Acroricnus and Osprynchotus, as well as chalcid wasps in the genus Melittobia, velvet ants in the genus Sphaeropthalma, and bee flies in the genus Anthrax. “Satellite flies” in the family Sarcophagidae, genus Amobia, are also a threat.

Look at an old mud dauber nest and you can decipher what happened to the offspring. A large hole chewed out at the end of a cell means an adult mud dauber successfully emerged. Small holes along the length of the cell mean some kind of parasite came out instead.

Once the new generation of wasps have emerged, the nests can serve as shelters for other insects or, ironically, retreats for spiders. Other wasps use the ready-made mud cavities for their own nests. Mason wasps like Ancistrocerus tuberculocephalus will partition an old mud dauber cell into at least two cells of its own.

Carpet beetle larvae will clean up any old spider and insect parts left over from all the tenants, and eventually the old nest may weather away, or be torn up by a mammal hoping for a juicy wasp larva snack.

It is impossible to address the many fascinating aspects of mud dauber biology in a single blog, so expect me to revisit this species in the future. Meanwhile, go see if any mud daubers have been busy on your own property. Chances are, they have been.

Mud Masterpieces

Solitary wasps are among the most amazing architects in the animal world, many of them creating beautiful nests in clay and sand. Each such dwelling will house a single offspring, provided with food in the form of paralyzed spiders, or insects of one sort or another. Sometimes more than one cell is created and the resulting multi-unit residence can be quite astonishing, too.

Perhaps my own personal favorites are the “potter wasps” in the family Vespidae, genus Eumenes. Females craft exquisite urns about the size of a marble, but usually complete with fluted “neck.”

She finishes one of these containers in its entirety before going off to hunt small caterpillars. She paralyzes several and stocks the pot with them. She then lays a single egg inside the clay sphere and seals the top with a final plug of mud. Inside, a larva hatches from the egg to find fresh food (paralyzed victims do not spoil like dead ones would). Once it has fed and matured, the larva molts into the pupa stage, and an adult wasp hatches a few weeks later, if the pupa is not overwintering for a longer period. The new adult chews a large exit hole in the side of the pot, crawls out, and flies off.

More commonly seen than potter wasp pots are they clod-like structures build by the black and yellow mud dauber, Sceliphron caementarium, in the family of thread-waisted wasps (Sphecidae).

The nests of this wasp are usually a cluster of several cells all covered in additional layers of mud. Some nests can be quite weighty, and thus are usually adhered beneath rock overhangs, or plastered under bridges and other man-made structures. Only one female is responsible for each nest, stuffing each cell with paralyzed spiders as food for the larva in each cell.

Another spider hunter is the aptly-named “pipe organ mud dauber,” Trypoxylon politum, family Crabronidae, found throughout most of eastern North America. Each female normally fashions two or more adjacent mud tubes, again adhered to a flat surface.

Each tube is actually a series of cells arranged in a linear fashion, partitioned on the inside. Trypoxylon are also spider-hunters, but in T. politum, they often work in pairs, male and female. While the female hunts or gathers mud, the male stays at home to defend the nest from potential parasites, predators, and rival wasps looking to usurp the rightful owners. The male has a wicked-looking hook on the underside of his abdomen that may help anchor him to the nest or substrate while doing battle. New nests of T. politum will be intact, while old nests will have large round exit holes down the length of each tube.

There is one other group of spider-hunting wasps that are accomplished masons. Spider wasps in the family Pompilidae, tribe Auplopini, construct delicate mud barrels to hold their spider prey and larval offspring.

Those in the genus Auplopus are small, with a widespread distribution. Phanagenia bombycina is a slightly larger wasp found east of the Rocky Mountains. Ironically, these wasps often build their mud cells inside the old nests of the pipe organ mud dauber.

Many people destroy the mud nests of wasps when they find them attached to their own home. They think the nests are an eyesore at best. Please consider tolerating them instead. Once finished constructing their nest, the female wasp goes off to build another somewhere else. She won’t “attack” even while building her nest. Solitary wasps are not at all aggressive like social wasps.

Those of you more scientifically inclined might consider “rearing” mud nests that you find. While you usually know what species will come out of one, there are many species of parasites that could emerge instead. Host-parasite relationships are not terribly well known, and you could make a significant contribution to science.