How to Manage Pests
Identification: Natural Enemies Gallery
Scientific name: Cotesia medicaginis
Cotesia medicaginis undergoes complete metamorphosis. The adult wasp is black and shiny with long antennae roughly 0.12 inch (3 mm) long. The female lays an egg in very small caterpillars. The shiny white wasp larva feeds within the caterpillar, killing it, and emerging to pupate in a cottony white cocoon.
A caterpillar parasitized by C. medicaginis may be recognized by being lighter than normal in color, somewhat shiny rather than velvety on the surface, and swollen toward the rear. Conspicuous evidence of Cotesia species is the white or yellowish coccoon.
You can also see the small, white, shiny Cotesia larva if you pull apart a parasitized caterpillar.