Wednesday, October 31, 2012

Wasp Wednesday: Wasps in a Bubble

One of the strangest inquiries I have ever received was the image below, from a Facebook friend named James Adams. He took the picture at the Rio Santiago Nature Lodge near Santa Ana, Honduras (northern coast). Not familiar with the tropical fauna there, I forwarded the image to Dr. James Carpenter at the American Museum of Natural History in New York City. Dr. Carpenter is a world authority on social wasps with much experience in the neotropics.

© James Adams

Here is the original post to James Adams’ Facebook page:

”OK so this is one of the weirdest things I've seen in nature. These small, black wasps created a normal-looking nest amidst leaves of a soursop tree. Then either they, or some other creature, encased the entire thing in this "plastic" bubble. Great protection from the rain, but WTH ????? There's a little oval-shaped hole in the bottom so they can get in and out. Anyone like Court Whelan or Deborah Matthews know what these wasps are called? Crazy! Rio Santiago Nature Resort, Honduras —“

Dr. Carpenter wrote the following in response to my query:

"It's a nest made by a species of Protopolybia. There are several species in the Amazon that make envelopes of "wax paper," such as chartergoides - you may encounter descriptions in the literature under the generic name Pseudochartergus. The paper that paper wasps make is most commonly wood fiber bound with saliva - these critters have just left out the wood."

The other comments on the original Facebook post of this image were delightful. Piotr Naskrecki, an extremely experienced explorer in his own right, said “Absolutely amazing, I have never seen anything like this.” Holly Overmyer was jealous: “I wish I could make a little plastic bubble when I get caught in the rain.” John Afdem quipped: “I'm just guessing here, but perhaps its one of the Saranwrapipedes???” Kenneth Barnett, not to be outdone, replied “John, you must talking about Polyrapus opaqous?”

James Adams runs The Lodge at Pico Bonito, La Ceiba, Atlantida, Honduras. I just may have to visit both nature lodges to see this kind of phenomenon for myself.

Sunday, October 28, 2012

Spider Sunday: Burrowing Wolf Spider

The story behind any given spider image can be quite interesting, and usually teaches the photographer a thing or two. I could not bring this one to you without the help of a number of individuals. The outcome is that I have finally seen a burrowing wolf spider in the genus Geolycosa. Is he not a handsome spider?

I was out with Heidi and some of our mutual friends on a geocaching adventure in the vicinity of Widefield and Security, just southeast of Colorado Springs in El Paso County on Monday, October 22. We stopped to find one cache at a particularly ugly ravine that was obviously used as a dump site. I won’t tell you about the surprising pieces of trash, but one member of our party, walking ahead of me, stopped, looking down, and called out to me. She had found a large spider crossing her path and was kind enough to point it out.

I recognized it as a wolf spider (family Lycosidae), and suspected it was a species in the genus Hogna. It seemed a little small, though. I took many pictures, few of which turned out to my satisfaction, but reviewing them I determined this was a mature male specimen, and it didn’t obviously fit anywhere in the genus Hogna. There is considerable variability in color and markings from one individual to the next, though, so I remained open-minded.

As luck would have it, it is “Arachtober” on, a group that accepts submissions of arachnid images only during the month of October each year. I posted my best image of the wolf spider and expressed my reservations about my identification. Another group member (and personal friend), Lynette Schimming, commented on my image and suggested it might actually be a male burrowing wolf spider, Geolycosa missouriensis. She included this link that shows a couple images of a male of that species. So, I have one Dan L. Johnson to thank now, too. Such is the circuitous route that spider identifications can take.

At least one of my references calls Geolycosa missouriensis the “Missouri Earth Spider.” Another lists it as the “Missouri Wolf Spider.” Indeed, the epicenter of its range is the Great Plains, from southern Canada to Texas, east to New York and west to Utah and Arizona. Like all members of the genus Geolycosa, it spends the majority of its life inside a deep burrow.

These are large spiders. Mature females measure about 21 millimeters, males 15-18 millimeters in body length. A sprawling male can span 34 millimeters. The front legs are stout, built to aid in digging, though most excavation is done with the powerful jaws (chelicerae). The front of the cephalothorax is much higher than the rear portion, which easily separates this genus from other wolf spiders.

Geolycosa missouriensis apparently has at least a two year life cycle, with half-grown individuals overwintering in burrows that may be a meter or more in depth (summer burrows average 20-25 centimeters). The vertical shafts are lined with silk, and enlarged as the spider grows. The mouth of the burrow may be ringed with a turret of silk mixed with debris.

Both genders mature in late summer or early autumn, and mating takes place at this time. Hence, the wandering male we found was likely looking for a spider spouse. Mated females lay their eggs in May or June of the following year. Each female prepares a spherical egg sac like other wolf spiders, and suns the parcel at the mouth of her burrow on warm days. Spiderlings do not disperse very far from their maternal home, so populations tend to be localized, and not easy to detect.

I may return to the area where we found this male sometime next year to look for the burrows of females. They prefer sandy soil in open areas with sparse litter that they incorporate into the turrets of their burrows. I hope I am lucky enough to encounter more of these charismatic arachnids no matter what the location.

Sources: Bercha, R. and R. Leech. 2011. “Geolycosa missouriensis,” Spiders of Alberta.
Evans, Arthur V. 2008. National Wildlife Federation Field Guide to Insects and Spiders of North America. New York: Sterling Publishing Co., Inc. 497 pp.
Fitch, Henry S. 1963. Spiders of the University of Kansas Natural History Reservation and Rockefeller Experimental Tract. Lawrence: University of Kansas. 202 pp.
Kaston, B.J. 1978. How to Know the Spiders (Third Ed.). Dubuque, IA: Wm. C. Brown Company Publishers. 272 pp.

Wednesday, October 24, 2012

Wasp Wednesday: Four-toothed Mason Wasp

Black-and-white animals are always attention-getters, and that goes for insects, too. Among the more conspicuous of those is the “Four-toothed Mason Wasp,” Monobia quadridens. This member of the family Vespidae, subfamily Eumeninae, is commonly seen at flowers during the summer and fall over most of the eastern U.S.

The common name of Monobia quadridens is somewhat puzzling, and I am not at all certain that it is “official.” It has also been called the “Carpenter Wasp,” and simply “mason wasp.”

This species ranges from southern Ontario and the entire eastern U.S. west to Kansas, New Mexico, and Wisconsin. It is also recorded in northern Mexico. Another species, Monobia texana, exists in Arizona and Texas.

The adult wasps are most often seen on flowers like goldenrod and thoroughwort. Males are easily distinguished from females by the big white spot on their face (females have entirely black faces). When not sipping nectar, the females are looking for nesting sites or hunting for caterpillar prey.

These are solitary insects, and each female selects her own nest location. Much of the time they utilize abandoned tunnels originally bored by the Eastern Carpenter Bee, Xylocopa virginica. Check for such nests along the edge of the roof of your own home. Monobia quadridens has also been observed to evict mason bees (Osmia sp.) from wood borings, killing the bee eggs, larvae, and pupae in the process (Byers, 1972). Abandoned nests of the Black and Yellow Mud Dauber may also be used by M. quadridens. Rarely, the old burrows of ground-nesting bees are used.

Male M. quadridens on sumac flowers

Once she selects a suitable nest cavity, the female wasp goes about hunting for prey. Considering the large size of the wasp, the caterpillars it hunts are rather small: Primarily leafrollers like the Sweetgum Leafroller, Sciota uvinella (family Pyralidae, subfamily Phycitinae); the Dimorphic Macalla Moth, Epipaschia superatalis and Maple Webworm Moth, Pococera asperatella (Pyralidae: Epipaschiinae); the Grape Leaf-folder, Desmia funeralis (Crambidae: Pyraustinae); Schlaeger’s Fruitworm Moth, Antaeotricha schlaegeri (Elachistidae: Stenomatinae); Psilocorsis sp. (Amphisbatidae); Platynota spp. (Tortricidae); and unidentified caterpillars in the family Gelechiidae.

Each caterpillar is stung into paralysis and flown back to the nest. Several caterpillars are stuffed into the bottom of the nest tunnel, and a single egg laid there. The female then collects a mud ball which she fashions into a curtain that seals off that compartment. She will leave a small empty “room” between that cell and the next one along the length of the tunnel, repeating the process for as many cells she can comfortably create. Once filled, the nest tunnel is sealed with a final plug of mud. The empty rooms, called “intercalary cells,” are thought to confuse parasites into thinking that nobody is home.

So, the sequence in a given nest, from the bottom up is brood cell, intercalary cell (empty), brood cell, intercalary cell, and so on, with a final intercalary cell nearest to the nest closure. This last empty cell is called a “vestibular cell.” There are generally less than five brood cells per nest.

Each female wasp may create more than one nest, as long as she is physically able to do so. Inside the nest, each egg takes about two days to hatch. The larva then begins consuming its larder of caterpillars. It takes an average of 4-8 days to finish eating before preparing for pupation.

The wasp larvae do not spin cocoons, but do secrete some kind of “varnish” that they apply over the interior walls of their cells in the course of one to three days. Each larva enters the inactive pre-pupal stage about five days after it finishes feeding. About three days later, the larva pupates (in summer generations; it may overwinter as a pre-pupa later in the year). Ten to twenty-one days elapse before an adult wasp emerges (again, for the summer generation). Males take less time to metamorphose than females. The eclosed (emerged) adult wasp then lingers inside its nest cell for another 2-3 days while its exoskeleton hardens and it is able to chew its way through the mud partition(s) to freedom.

Not all make it, of course. Some orient themselves the wrong way during the pre-pupal stage and are not able to turn around inside their cells once they emerge as adults. Others are victimized by parasites. Mites (Tortonia quadridens and Monbiocarus quadridens), may take a toll, even though they are thought to be scavengers that feed on the remains of the caterpillar prey inside the cells. The larval stage of the bee fly Anthrax aterrimus feeds as an external parasite on the pre-pupal or pupal wasp. Larvae of Amobia erythrura, a “satellite fly” in the family Sarcophagidae, eat the caterpillars stored for the wasp larva, essentially starving it to death. Melittobia chalybii are tiny parasitic wasps in the family Eulophidae that lay their eggs in the larva of the host. This includes Monobia quadridens.

My good friend Joe Cohelo made a nice little video about these wasps. He includes some quality still images at the end. Much remains to be learned about this wasp despite previous studies, and your own observations, videos, and images could help increase our collective knowledge. Personally, I like the idea that these mason wasps can get to leaf-rolling pests even when chemical applications can’t easily penetrate the caterpillars’ refuges. It just goes to show that nature has its checks and balances, and sometimes we should let them operate on their own schedule.

Sources: 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).
Byers, George W. 1972. “Competitive Supersedure by Monobia quadridens in Nests of Osmia lignaria,” J Kans Entomol Soc 45(2): 235-238.
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.

Sunday, October 21, 2012

Spider Sunday: Butterfly Orbweaver

Most of the orb weaver spiders that you see at this time of year are enormous mature females that sit in the center of their webs. Not all members of the family Araneidae are so large, however. A case in point is a species that I found right outside the back door of the house we rented in Cape May, New Jersey earlier this month.

I noticed one of these spiders during the day, huddled in a depression in the eave of the house, next to an egg sac. I took a picture and noticed the ornate, butterfly-shaped pattern on the spider’s abdomen. Once I returned home I was not surprised to find the common name of the species to be the “Butterfly Orbweaver,” Araneus pegnia. Older references use the name Neosconella pegnia.

The “butterfly” can be pinkish or gray or brown or yellowish, varying from specimen to specimen. The entire spider, even as an adult, is not very big. Mature females are only 3.5-8.2 millimeters, and males like the one below are even smaller, 2.5-5 millimeters.

I found that this species is most active at night. At least three specimens, two females and one male, made their living around the back porch light, where many small insects were attracted each evening. The odds of catching prey were obviously increased given this situation. I could never clearly discern the structure of the webs, or whether they were even complete, but references suggest the orbs are at least sometimes incomplete anyway. The circular snare may be missing a sector, with a bundle of signal threads running up to the spider’s retreat on the perimeter. The orb may also be complemented by a network of irregular threads similar to those of labyrinth orbweavers. I did find one female sitting in the hub (center) of her web on one evening, as depicted in the image at the top of this post. Another female was busy creating her web (below).

The lone male I found (image above) was literally hanging out, but perhaps his duty was done. One of the females was already protecting an egg sac. The ova appeared to be obvious, as a ball covered by several layers of opaque silk.

Many of the female’s offspring will not survive to maturity, or at least not live until the first hard frost that kills most late-season orb weavers. The Butterfly Orbweaver is apparently a favorite prey item for the Black and Yellow Mud Dauber wasp, Sceliphron caementarium. The victimized spiders are paralyzed by the wasp’s sting and stuffed into a mud cell as food for a single mud dauber larva.

Araneus pegnia is a far-ranging species. It occurs from at least as far north as Massachusetts, south and west to Ohio and Indiana, the Atlantic and Gulf Coast states, and southern Arizona and California. It is perhaps most common in the southeastern U.S. Outside of the U.S. it ranges to Ecuador in South America. It is also found in the Bahamas, Cuba, and Jamaica. The preferred habitat seems to be in wet areas (bogs in Massachusetts, a river bottom in Costa Rica, for example).

It is certainly easy to dismiss these diminutive spiders as simply immature versions of a larger species, so pay close attention when spider hunting. Autumn is the perfect time to find many kinds of orb weavers, as the leaves fall and their webs are more exposed; and most species have reached maturity.

Sources: Gaddy, L.L. 2009. Spiders of the Carolinas. Duluth, MN: Kollath+Stensaas Publishing. 208 pp.
Howell, W. Mike and Ronald L. Jenkins. 2004. Spiders of the Eastern United States: A Photographic Guide. Boston: Pearson Education. 362 pp.
Levi, Herbert W. 1973. “Small Orb-weavers of the Genus Araneus North of Mexico (Araneae: Araneidae),” Bull Mus Comp Zool 145(9): 473-552.

Wednesday, October 17, 2012

Contest Announcement

Just in time for the holiday gift-giving season, I am announcing a contest. Anyone who has donated to my Bug Eric blog or Sense of Misplaced blog (or my account) between the first of this year and November 30, 2012 will have their name entered into a drawing. The prize will be a signed copy of the Kaufman Field Guide to Insects of North America. Minimum donation is $5.00 US, please. In the event that a person makes more than one donation, their name will be entered for each donation. Thank you, and good luck!

Wasp Wednesday: Anoplius aethiops

The western states may have the giant “tarantula hawks,” but most of the U.S. and adjacent Canada has another fierce spider wasp in the family Pompilidae. On our trip to Cape May, New Jersey, September 30-October 5, we encountered several big females of Anoplius aethiops. Ok, they were most likely that species, but it requires microscopic examination to separate them from the similar Anoplius cleora.

The first one I saw was so large that I at first mistook it for a Great Black Wasp, a wasp in an entirely different family. Both wasps are large, jet black, with black wings that reflect blue or violet. The spider wasps do not, however, have the abdomen separated from the thorax by a thin petiole (stalk). When I got a side view of the wasp, it became clear it was not in the genus Sphex. Still, it goes to show how difficult it is to identify insects in the field.

Female Anoplius aethiops measure 13-23 millimeters in body length, males 9-18 millimeters. Though black in color, their bodies reflect a hint of bluish or purplish color in the right light.

My “Spider Sunday” post was about a species of large wolf spider, the kind that these big spider wasps target. Each female Anoplius aethiops digs her own burrow, usually originating inside an existing burrow or crevice, and then goes off to find a spider to stash inside the tunnel. Heidi and I encountered one female wasp toting a good-sized wolf spider down the path we were on in Cape May Point State Park.

The wasp was walking backwards quite rapidly, while using her jaws to hoist her heavy prey completely off the ground. This feat of strength would be like you or me lifting a recliner with our teeth and backing across the street.

The spider is not even dead, but only paralyzed by the wasp’s venom when she stung it in a nerve center. Unfortunately, even in my rather careful efforts to get more images of wasp and spider, she ended up abandoning her prize. An abandoned, paralyzed spider may or may not eventually “come to” from its comatose state.

All known host spiders for Anoplius aethiops are lycosid wolf spiders: Hogna helluo, H. carolinensis, H. aspersa, H. baltimoriana, H. frondicola, Rabidosa santrita, Gladicosa gulosa, and Schizocosa ocreata. Once she places a spider in the bottom of her underground nest, the wasp lays a single egg on the spider, exits, and then closes the burrow. She will repeat the process as long as she is able. This is a wasp most common in late summer, and persisting into late fall. Most of the specimens we saw in New Jersey had tattered wings, indicating they had been active for quite some time already.

Look for Anoplius aethiops in open areas like fields, forest edges, meadows, and prairies. It tends to be replaced by A. cleora in open sand dune habitats. Both genders visit flowers such as wild carrot, goldenrod, sweet clover, milkweed, and throughwort for nectar. Anoplius cleora rarely visits flowers, so that is another way to distinguish the two species.

This wasp ranges coast to coast in the United States, save for North Dakota, plus southern British Columbia and southeast Canada to the north; and Mexico and Guatemala to the south. It is apparently less common in the southeast U.S. than in other parts of its range. Late July through mid-September is the typical seasonal range for this wasp.

Sources: Evans, Howard E. 1951. “A Taxonomic Study of the Nearctic Spider Wasps Belonging to the Tribe Pompilini (Hymenoptera: Pompilidae) Part II: Genus Anoplius Dufour,” Trans Am Entomol Soc LXXVI, 207-361.
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): 67-119.
Kurczewski, Frank E. 1975. “Host Records for Some Species of Pompilidae From the Southwestern United States and Mexico,” Pan-Pac Entomol 51(2): 147-151.
Kurczewski, Frank E. and Edmund J. 1968. “Host Records for Some North American Pompilidae (Hymenoptera) With a Discussion of Factors in Prey Selection,” J Kans Entomol Soc 41(1): 1-33.
Kurczewski, Frank E. and Edmund J. and Roy A. Norton. 1987. “New Prey Records for Species of Nearctic Pompilidae (Hymenoptera),” J Kans Entomol Soc 60(3): 467-475.
Wasbauer, M.S. and L.S. Kimsey. 1985. “California Spider Wasps of the Subfamily Pompilinae (Hymenoptera: Pompilidae),” Bulletin of the California Insect Survey vol. 26, 130 pp.

Sunday, October 14, 2012

Spider Sunday: Dotted Wolf Spider

Large wolf spiders (family Lycosidae) are normally difficult to spot, given their habit of prowling on the ground amid tangles of grasses and other vegetation. Imagine my surprise, then, to find one stretched out on grass stems about three feet off the ground. I recognized it as a normally ground-dwelling member of the genus Rabidosa, and I think I know what it was doing up there.

There are five species in the genus Rabidosa that occur in North America, and I was pretty sure it wasn’t the common “Rabid Wolf Spider,” Rabidosa rabida. It was mature, but not that large, and it lacked the pale spots inside the margin of the dark chocolate stripe down the abdomen. Twisting the grasses for a better picture caused it to reveal its underside, and then I remembered that the underside of the abdomen also has a diagnostic pattern of black spots or blotches.

Once I got home, I discovered the spider was a mature female “Dotted Wolf Spider,” Rabidosa punctulata. This particular individual was found at the edge of an open agricultural field in an otherwise wooded area in the Higbee Beach Wildlife Management Area, Cape May, New Jersey, on October 4, 2012. The species ranges from Massachusetts and southern Michigan, south to northern Florida, southeast Kansas, and eastern Oklahoma and Texas.

Mature female Dotted Wolf Spiders measure an average of 15.2 millimeters in body length, while males are about 12.8 millimeters. Adults, at least females, mature between June and October. Mature males appear in early September, but are thought to mature earlier in the year. The male follows the pheromone-impregnated draglines of females.

Recent research has revealed that males of R. punctulata have two alternative mating strategies. Large specimens in good physical condition simply overpower a potential mate, grappling with her until she submits to copulation. I know, that sounds a lot like rape to me, too! Smaller males, or those in poorer condition, go through full courtship displays that involve leg-waving, and stridulation with the pedipalps that cause rhythmic vibrations picked up by the female being courted (see this website).

Mated females take three or more hours to create an egg sac that they attach to their spinnerets, allowing them to continue a nomadic lifestyle. She probably totes her brood this way for about a month. The spiderlings that emerge then pile atop the female’s abdomen, latching onto knob-tipped hairs where they ride until their next molt (roughly three weeks later, extrapolating from data on R. rabida). I could find no reference to exactly when females carry their egg sacs, but presumably it is in late autumn, the spiderlings overwintering in protected places.

These spiders prey on a variety of insects, including small grasshoppers, but may scavenge dead insects as well. Most references indicate that this species is a nocturnal hunter, and mostly waits in ambush for an insect to wander within pouncing range. They may also run down their prey. Prey is seized with the legs, helped by sticky brushes of hairs on their legs. The spider may loosely wrap its prey in silk to help secure it from falling to the ground if the spider is resting on vegetation.

So, what was my spider doing, up a tree in essence, without prey? Avoiding becoming prey itself is my theory. I also observed a large spider wasp, Anoplius aethiops or A. cleora, scouring the ground for potential wolf spider prey in the vicinity of this spider. I suspect the spider beat a hasty retreat out of reach of the typical search zone for the wasp.

Note: This species was formerly known as Lycosa punctulata, and older references will use that name. It has since been determined that Lycosa is an Old World genus with no species in North America.

Sources: Brady, Allen R. and Kelly S. McKinley. 1994. “Nearctic Species of the Wolf Spider Genus Rabidosa (Araneae: Lycosidae),” J Arachnol 22: 138-160
Eason, Ruth Robinson. 1964. “Maternal Care as Exhibited by Wolf Spiders (Lycosids),” Arkansas Academy of Science Proceedings, vol. 18: 13-19.
Fitch, Henry S. 1963. Spiders of the University of Kansas Natural History Reservation and Rockefeller Experimental Tract. Lawrence: University of Kansas Museum of Natural History, Miscellaneous Publication No. 33. 202 pp.
Howell, W. Mike and Ronald L. Jenkins. 2004. Spiders of the Eastern United States: A Photographic Guide. Boston: Pearson Education. 363 pp.
Moulder, Bennett. 1992. A Guide to the Common Spiders of Illinois. Springfield, IL: Illinois State Museum Popular Science Series, Vol. 10. 125 pp.
Wilgers, Dustin J. 2012. “Courtship signal evolution in Rabidosa Wolf Spiders.”.

Wednesday, October 10, 2012

Wasp Wednesday: The "Horse Guard"

Heidi and I were away last week in Cape May, New Jersey for a belated honeymoon, celebrating in the same place we had our first “date” back in October, 2010. We went a week earlier this time, and visited some locations we had missed on our last trip. Consequently, we saw some different birds and insects, including a wasp that was on my “bucket list.”

The Triangle Point Butterfly Garden, a tiny park near Cape May Point State Park, is planted with a variety of native and exotic flowers that attract many kinds of insects. We visited in the early afternoon of October 5, and found another party looking at the butterflies, but wondering what the big black and white wasps were.

”Oh, my God, that’s a Horse Guard!” I couldn’t contain my enthusiasm as I frantically focused my zoom lens on the wasp. I had forgotten that Stictia carolina, the largest of our “sand wasps” aside from cicada killers, ranged this far north, and persisted into the autumn months.

The Horse Guard is found from New Jersey and Pennsylvania south to Florida and west to Illinois, Kansas, and New Mexico (barely). It is most abundant in the southern Great Plains. Though solitary, each female excavating her own nest, many wasps may nest in a small area of sandy soil.

How did the Horse Guard get its name, you might ask? Also known as “cowfly tigers” and “insecto policia,” the wasps are specialist predators that chiefly attack horse flies. Naturally, the best place to hunt horse flies is around equines. The female wasps will fly around a horse, up and down each leg, searching for their prey. They can even fly backwards in front of a moving horse. This hunting behavior is frequently interpreted as aggression by “hornets” by the average, intimidated horseback rider or ranch hand. Once people understand the intent behind the wasps’ persistent hovering, the usual reaction is one of relief and elation.

”That’s fantastic! How can I encourage more of these wasps for horse fly control?”

Short of importing a sand dune, as the late Howard E. Evans writes in his book Wasp Farm, there is very little one can do to ensure the presence of horse guards at any given farm or ranch. The best thing to do is simply not kill them or accidentally obliterate their nesting areas.

Males search for females by engaging in “sun dances,” which are level flights in circles, figure eights, or sinuous patterns, occasionally perching on low herbs, dung, stones, or on the ground. These patrol beats are most often in the vicinity of female nesting areas, and usually in the morning hours. They will actively chase each other, or molest other large insects that pass through their individual territories.

Females take a surprisingly long time to complete a burrow, taking an average of 22-30 hours. Burrows are usually initiated in the morning, with frequent breaks as the sun becomes more intense, with digging activity increasing again in the late afternoon. The wasp closes the tunnel each time she leaves the vicinity. The burrow is a diagonal excavation, averaging 35-51 centimeters in length, and to a depth of 18-24 centimeters. Soil properties influence these numbers. The tunnel terminates in a single cell, where the wasp deposits a single egg.

Once the nest is completed, the wasp begins hunting, feeding her larval offspring in the progressive fashion that birds do. Between visits, the wasp makes both an inner closure that seals off the terminal cell, and an outer closure that obscures the nest entrance at the surface. Fifteen to thirty-five flies may be fed to the average wasp larva during its lifetime. Larger flies (like horse flies), mean fewer flies are necessary to feed a growing larva. Still, the hunting tactics of the wasps can be very effective in protecting livestock from blood-sucking flies.

The double closure of the burrow between the frequent visits by the mother wasp helps eliminate many of the opportunities parasites usually use to gain entry into sand wasp nests. “Satellite flies” in the family Sarcophagidae (subfamily Miltogramminae) do deposit their own tiny larvae on the prey carried into the nest by the female Horse Guard, but those larvae are generally content consuming the leftovers of prey, rather than attacking the wasp larva itself.

Interestingly, while I was employed by the Cincinnati Zoo in 1988, we received pupae of horse guards from Mississippi that yielded both the expected wasps, but also “Cow Killer” velvet ants, Dasymutilla occidentalis. This would imply that occasionally the Horse Guard offspring fall prey to larvae of velvet ants.

There are two other species of Stictia in the southern U.S., but even more in the New World tropics (28 species total).

Look for the Horse Guard if it ranges in your part of the U.S. All the specimens imaged here are females, by the way. Males, active much earlier in the season, have the white markings confined to the front half of the abdomen only.

Sources: Bohart, R.M. and A.S. Menke. 1976. Sphecid Wasps of the World: A Generic Revision. Berkeley, California: University of California Press. 695 pp.
Evans, Howard E. 1966. The Comparative Ethology and Evolution of the Sand Wasps. Cambridge, Massachusetts: Harvard University Press. 526 pp.
O’Neill, Kevin M. 2001. Solitary Wasps: Behavior and Natural History. Ithaca, New York: Comstock Publishing Associates (Cornell University Press). 406 pp.
Pulawski, Wojciech J. 2011. “Catalog of Sphecidae sensu lato,” California Academy of Sciences

Friday, October 5, 2012

About the BioQuip ad....

There is little that one gets for free these days, and indeed I could not continue to produce my blogs without help from various individual and corporate benefactors. While my readers probably like the fact there is minimal advertising on this website, financial realities demand that I seek additional advertisers. I have high standards, however, and will not endorse any product or service that I do not believe in, and/or have not personally worked with. That is why I am proud to have the BioQuip button on my page.

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Their current headquarters in Rancho Dominguez, California include a retail store on the premises, as shown in the image above. I highly recommend BioQuip for quality scientific merchandise and specimens. Consider them as a one-stop shopping gift center for the entomologist on your holiday list. You will not be disappointed. Please visit the online catalogs at and (formerly Combined Scientific), or simply click on the ad to the right in this blog.

BioQuip Bugs at the 2011 Los Angeles "Bug Fair"

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