Family Gasteruptiidae - Wasp - Gasteruption sp.

Family Gasteruptiidae - Wasp - Gasteruption sp. Male and female adult imagines
Host plant: Wild parsnip (Pastinaca sativa)
Hymenoptera / Apocrita / Evanioidea / Family: Gasteruptiidae - Parasitic Wasps / Subfamily: Gasteruptiinae
Live adult male and female wasps photographed in the wild at Winfield, Illinois, USA.
Genus Gasteruption contains over 400 species.

Parasitic Wasp
Female wasp takes nectar, ignoring two ants engaged in the same activity.

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 sewing needle) voraciously nectaring at wild parsnip (Pastinaca sativa) - 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. I'd venture to say if you're looking for these wasps, look for parsnip-family plants.

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

Male and female Gasteruptid Wasps
A male wasp (left) continuously dogged the female. She rebuffed his every advance.

Female length: 25mm including ovipositor excluding antennae	Female, dorsal view
	Male and Female Imagines
	Male: 15mm not including antennae

Wild parsnip (Pastinaca sativa) is an eye-catching, non-native weed that hails originally from Europe and Asia. Wild parsnip grows in large patches or as scattered plants along roadsides, in abandoned fields, on pastures, on restored prairies, and in disturbed open areas. According to this article, wild parsnip can cause chemical-type burns on exposed human skin. News to me. I've spent probably fifty or more hours shooting insects on this plant, and I have never experienced any adverse reactions.

"There are chemicals in wild parsnip called psoralens (precisely, furocoumarins) that cause what dermatologists call "phyto-photo-dermatitis." That means an inflammation (itis) of the skin (derm) induced by a plant (phyto) with the help of sunlight (photo). When absorbed by skin, furocoumarins are energized by ultraviolet light (present during sunny and cloudy days) causing them to bind with nuclear DNA and cell membranes. This process destroys cells and skin tissue, though the reaction takes time to produce visible damage."
- From "Burned by Wild Parsnip" - Wisconsin Natural Resources Magazine

	Insects LOVE this plant. I only know of one patch of these plants at the Winfield Mounds Forest Preserve, and I spend a lot of time there when the yellow weeds are in bloom. They attract almost every variety of insect in search of nectar. Here are pictures of just a few of the larger ones - I don't bother usually with small ants and tiny beetles, of which there are thousands competing for space at the trough. Clockwise from far right: spotless lady beetle; Brachicantha ladybug; soldier beetle; Archytas fly (Tachinidae); 7-spotted ladybug; Sphecid wasp; Ichneumon wasp; Virginia ctenuchid moth. Quite a variety of pollinators.