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How to Manage Pests

Identification: Natural Enemies Gallery

Cotesia medicaginis

Scientific name: Cotesia medicaginis

Life stages of Cotesia medicaginis

Click on image to enlarge

Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Braconidae

Common hosts: Alfalfa caterpillar in alfalfa

Commercially available: No


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.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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