Agenioideus humilis

Distinguished from other spider wasps by the combination of small size, dull black coloration, and the white dorsal spot on the hind tibia. The wing pattern—clear with dark edges and a broad dark band on the forewing—provides additional diagnostic characters. Males are notably smaller and differently proportioned than females. The species lacks the bright coloration or metallic sheen seen in many larger pompilids such as tarantula hawks (Pepsis spp.).

Small, dull black wasp with clear wings bearing dark edges and a broad dark band on the forewing. Females measure 5.5–10.5 mm in body length (averaging 8 mm); males are smaller at 4–9.5 mm (averaging 6.5 mm). Both sexes display a distinctive white spot dorsally near the base of the tibia on the hind leg. Males have a substantially smaller and different body type than females.

Woodland habitats with sandy soil; mixed coniferous forest with understory shrubs including oak and chokecherry. Nesting occurs in sandy substrates, including soil excavations and pre-existing cavities in rocks or building walls.

United States, excluding the northern Rocky Mountains, northern Great Plains, most of Minnesota, Wisconsin, and northern Michigan. Nowhere common; scarce in collections throughout range.

Adults do not appear to feed on flower nectar or aphid honeydew, unlike most adult spider wasps. Larvae are parasitoids that feed on paralyzed orbweaver spiders.

• Araneidae - preyOrbweaver spiders including Acacesia hamata, Larinioides cornutus, and Araneus pegnia

Female paralyzes a single spider with her sting, transports it to a nest site, and excavates a burrow or uses a pre-existing cavity. A single egg is laid on the spider, the entrance is concealed with soil scraped and compacted using abdominal blows, and the female departs to repeat the process. Larva develops by feeding on the paralyzed host.

Females hunt actively, dragging paralyzed spiders to nest sites even when disturbed. Nesting involves rapid digging with soil ejected between the legs. Males have been observed loitering near nesting females, possibly seeking mating opportunities. The wasp maintains grip on prey during transport and will continue descent even when startled.

Predator of orbweaver spiders; population control of Araneidae. Acts as a parasitoid with single-host provisioning strategy. Contributes to nutrient cycling through subterranean nesting activity.

Minimal direct interaction with humans. Nesting in building cracks may bring it into occasional proximity with human structures. Not known to sting humans unless handled. Of interest to entomologists due to scarcity in collections and specialized hunting behavior.

• Agenioideus nigricornisAustralian congener that hunts cobweb weavers (Theridiidae) including the dangerous Redback Spider (Latrodectus hasselti); differs in geographic range and prey family
• Pepsis spp.Larger, brightly colored tarantula hawks with metallic blue-black bodies and orange wings; differ dramatically in size, coloration, and prey (tarantulas and large spiders)
• Tastiotenia festivaAnother small spider wasp with circumstantial record as potential predator of widow spiders; differs in restricted southwestern U.S. range and less well-documented biology

• spider wasp
• Pompilidae
• parasitoid
• orbweaver predator
• solitary wasp
• ground-nesting
• rare in collections

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
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