Surprisingly, you may find some wasps at your porch light after dark. Among the more common nocturnal hymenopterans are ichneumon wasps in the subfamily Ophioninae. They are large, gangly wasps, usually uniformly orange in color with long antennae and large ocelli (“simple eyes” arranged in a triangle at the crown of the head, between the compound eyes). The ovipositor is very short, if it is even evident at all.
If you see a slightly smaller orange ichneumon with a longer ovipositor, it is likely to be a wasp in the genus Netelia, in the subfamily Tryphoninae. There are currently 73 species in six subgenera in North America north of Mexico (Carlson, 2009).
Unlike many ichneumon wasps, the females of Netelia can sting painfully if handled carelessly. The sting is mostly used to temporarily paralyze the large caterpillar hosts of these parasites. The female then lays an egg on the stunned victim, puncturing the body wall of the caterpillar in doing so. The egg is stalked, and in newly deposited eggs the coil of the stalk is elastic. It later becomes rigid. The egg holds firmly to the flexible exoskeleton of the host larva by means of a plug or anchor.
The larval wasp that hatches from the egg remains attached to it via specialized bristles on its posterior end. The wasp larva feeds on the caterpillar as an external parasite. Parasites that do not arrest the development of their host, but allow it to grow normally instead, are called “koinobionts.” Netelia ichneumons are placed in this category.
Below is an example of an ichneumon in the subfamily Ophioninae for comparison to Netelia.
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