Spider Wasp - Ecology and Behavior

Ecology and Behavior

Currently, the Pompilidae are split unequally into six subfamilies throughout most of the world. Ceropalinae and Notocyphinae contain two genera each and occur in Central and South America and the Oriental region. The Epipompilinae contain a single genus and occurs in the Neotropics, the Australasian region, and the Afrotropical region. The Ctenocerinae contain two genera in the Neotropics, four in Australia and 11 in Africa. Pepsinae and Pompilinae are the most diverse, and the remaining genera are split between them.

As mentioned above, the Pompilidae get their common name, “spider wasps”, from their notable behavior of hunting and killing spiders, often larger than themselves, as food for their larvae. They provide each of their larvae with a single prey/host, which must be large enough to serve as its food source throughout its development. Pepsis thisbe of the southwestern United States exibits a direct correlation between adult wasp body length and the weight of its host spider, Aphonopelma echina. Because the size of a P. thisbe adult is determined by the size of the host provided for it by its mother, the seasonal frequency of host sizes implicitly will determine the size variation in adult wasps.

Because of the large body size of their prey, pompilids usually will either construct burrows near the site of attack or use the host’s own burrow or tunnel. The paralyzed spider is concealed in a burrow so larva can develop without disruption by other parasites or scavengers. Some pompilids only temporarily paralyze their hosts, which regain activity before being killed by the maturing wasp larva.

In another study on Pepsis thisbe, chemosensory cues were shown to be used to detect specific hosts. Specific chemosensory cues attract the wasp to its prey, Aphonopelma echina, despite other host spiders of the same size and frequency being present.

In studies on Pepsis formosa, a pompilid of the southwestern United States, the wasps were found to have behavioral plasticity. Their hunting behavior concerning their host Rhechostica echina improved with experience. The time required to complete all behavioral components decreased with each spider killed.

Concerning mating behavior, males acquire perch territories to scan for incoming receptive females. In studies on the tarantula wasp Hemipepsis ustulata, larger males are more likely to acquire perch territories and territorial males appear to increase their chances of mating because receptive females fly to perch sites held by said males.