Gasteruptid Wasp - Gasteruption sp. Male and female adult imagines
Family: Gasteruptiidae - Parasitic Wasps
/ Subfamily: Gasteruptiinae
Live adult male and female wasps photographed in the wild at DuPage County, Illinois. 

Parasitic Wasp

Bees & Wasps Index | Bees & Wasps Main | Aculeata - Bees, Ants, and Stinging Wasps
Wasps in the family Gasteruptiidae are predator-inquilines that lay eggs inside the cells of solitary bees and wasps nesting in plant stems or in underground nests, with the resulting larvae feeding on the food stores and/or nest inhabitants. The ovipositor on this female wasp is not used for drilling into wood, as in some other parasitic wasps (see Megarhyssa), but is used as a sort of remote placement device; the wasp inserts it into an existing nest or burrow. I won't reinvent the wheel; Tree of Life Web Project has a thorough write-up on these curious insects.

Adult Gasteruptiidae wasps feed on flower nectar, and at least some are believed to eat pollen as well. I found these very slender (imagine an insect almost as thin as a darning needle) voraciously nectaring at wild parsnip, sharing the nectar source with various tachinid flies, beetles, lady beetles, ichneumon wasps, sawflies and ants. Only the female wasps were feeding - the males did nothing but follow the females around. (Sound familiar?) The Insects of Cedar Creek says these wasps are often collected on water hemlock - a member of the Parsnip family.

Parasitic Wasp
Female wasp is fully 1 inch long, but nearly as thin as a darning needle; it is difficult to follow her frenetic nectar-gathering.

Male and female Gasteruptid Wasps
A male wasp (left) continuously dogged the female.

Wasp Nectaring
Female length: 25mm including ovipositor excluding antennae

Gasteruptiid Wasp Male

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Order Hymenoptera: Bees, Wasps, & Ants
Hymenoptera (Latin for membrane wing) is a vast assemblage of insects second only to Coleoptera (beetles) in the number of described species. Hymenoptera number some 115,000 species - of which 18,000 live in North America. Hymenopterans inhabit a wide variety of habitats, and show an incredible diversity in size, behavior, structure and color.
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