Cotesia Wasps
(Common Name)
(General Category)
Hymenoptera: Braconidae
(Taxonomic Classification)
Cotesia congregata
(Scientific Name)

Cotesia wasp adult with rollover ID charactersCotesia wasp larvae with rollover ID characters

Description: These wasps are common parasitoids of hornworm caterpillars that are often seen in home gardens. Adult females inject their eggs into hornworm caterpillars. The eggs soon hatch into grub-like larvae that feed a week or two on tissues inside the hornworm hosts. Their small size allows many larvae to be accommodated by each caterpillar. When they are done feeding, the larvae chew small holes in the skin of their host and squeeze through so they can spin silk cocoons and pupate attached to the outside of their still-living host. These cocoons are often mistaken for eggs. After this point the caterpillar feeds very little, and can be viewed as a nursery for these beneficial parasitoid wasps. Within about a week, the adult wasps emerge, and a day or two after that the caterpillar host dies.

Identification:  Rollover pictures with mouse for tips on how to identify these parasitoids. Adults: These parasitoid wasps usually have very long, thin antennae, 4 usually dark wings, long, thin legs, wasp-like bodies. Braconid wasps are closely related to the ichneumonid wasps that also attack caterpillars. These two groups have very similar appearances, but can be separated by the pattern of veins in their wings. When they alight on a plant, notice they have 4 wings (as opposed to only 2 in flies). Larvae: Grub-like in appearance, hidden inside their host insect until they are done feeding and emerge to pupate. See video of another Cotesia species larvae inside a caterpillar.

Value in Pest Management:  These parasitoids are common natural control agents of several native hornworm caterpillars, including tobacco and tomato hornworms. They undoubtedly contribute to population regulation of these pests. Adults will feed on and benefit from nectar-producing flowering plants, and have been considered in some conservation biological control studies. They are not sold commercially.

Origin and Distribution:  Native, throughout eastern North America ( ).

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