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.

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.”.

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

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