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.
A male wasp (left) continuously dogged the female.
Female length: 25mm including ovipositor excluding antennae
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 vs. 350,000 in Coleoptera. 18,000 of these species call North America north of Mexico home. Hymenopterans inhabit a wide variety of habitats, and show an incredible diversity in size, behavior, structure and color.
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