Pompilidae - Agenioideus biedermani
Size: 11 mm (female)
Group Guild Status
Trogloxene Parasite Rare
Pompilid (spider) wasps are external parasites (as larvae) of various spider species. Few pompilids are plastic in their prey selection, with most species preying on a single species or family of spiders. At least one species (Ageniella evansi) is more flexible (or opportunistic) in its prey selection, and take prey from several families of spiders (RBP, unpublished data). The only prey record for A. biedermani is on the sicariid (brown spider) Loxosceles devius in Texas (Evans 1959). A. biedermani is known from California east to Kansas and south to the State of Hidalgo, Mexico (Wasbauer and Kimsey 1985). This species is known in Kartchner Caverns from a single dead individual that was found on August 14, 2010. The animal was found high in the top of the Tarantula Room on the floor below the location where the first live thread-legged bug (Phasmatocoris labyrinthicus) was observed that same day. The Mutillid wasp record was from this same location. We suggest there is some potential that this animal may also have been prey of the thread-legged bug. During their foraging efforts for suitable prey female pompilid wasps search along the ground for spiders. Depending on the prey species that are hunted the wasps also search among vegetation, beneath objects on the ground, in animal burrows, in earth cracks and in caves (Evans and Shimizu 1996; RBP, personal observation). Many species place their prey in cells in the ground, some excavating small side tunnels off of rodent burrows (Evans and Shimizu 1996; Kurczewski and Kurczewski 1987). It is therefore not unusual for some species of pompilids to enter caves either to seek prey or rarely, to nest. The presence of a species of Loxosceles in Kartchner Caverns along with an individual of A. biedermani may be evidence that this wasp occasionally hunts in caves. Because of the occurrence of the sicariid spider and the wasp in the cave, we consider A. biedermani to be a potential trogloxene in the cave, where it may hunt for its spider prey.
Interestingly, the dead wasp was partially entangled in strands of spider silk when it was found lying on the floor of the cave. So, there is some potential that it had been prey for a spider, although no spiders or active webs were found in the immediate area at the time. The wasp was not encased in the silk to the degree prey are usually “wrapped” by spiders, but it appeared more like the animal had become tangled in some old spider web silk. Another possibility for the demise of the wasp was that there may be involvement with the thread-legged bug using old spider web remnants as trip wires to locate prey. Several species of emesines are intimately involved with active or abandoned spider webs that are used in prey capture, and a few species actually have evolved adaptations for the manipulation of spider silk (Wygodzinsky 1966). RBP observed one of the cave emesine bugs apparently situating itself at the edge of a spider web remnant directly above the location where the dead A. biedermani was found on the floor of the cave. If enough of a spider web were present, the wasp could have become entangled in the web remnants, making it that much easier for the emesine to capture and subdue it. Additional comments on this are found in Pape (2013).
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