Parasitoid Wasps

Order: Hymenoptera
Family: Braconidae, Ichneumonidae, Eulophidae, Aphelinidae, Trichogrammatidae 


These wasps are a large and diverse group of parasitoids. Most are extremely small, under 0.5-inches long and attack small insects such as aphids.

Giant ichneumon wasp (Rhyssa persuasoria)

Boris Hrasovec, Faculty of Forestry, 
Giant ichneumon wasp Rhyssa persuasoria.

Braconid wasp cocoons on a tobacco hornworm

Clemson University – USDA Cooperative Extension Slide Series, 
Braconid wasp cocoons on a tobacco hornworm.

Aphid parasitoid wasp

Frank Peairs, Colorado State University, 
Aphelinus sp.Aphid parasitoid wasp.

Quick Facts

  • Beneficial arthropods can prevent or limit pest problems in the yard and garden. 
  • These beneficial wasps can be categorized broadly as either insect predators or parasites.
  • Common insect parasitoids include flies and small wasps. 
  • When insecticides are needed, choose ones that are selective and less likely to harm beneficial insects and mites. 


Additional Information


Life History

Usually, female wasps parasitize hosts by paralyzing an adult insect or larva and laying eggs inside. Upon hatching, the wasp larvae feed on and eventually kill the host insect. Important aphid parasitoids include members of the families Aphelinidae and Braconidae. Larger parasitoid wasps attack caterpillars or wood-boring beetles. Wasps in the family Trichogramma are commonly used for biological control as well and many can be commercially purchased.  

Gardeners are more likely to see the results of parasitoids’ activities, rather than the wasps themselves. For example, aphids that are parasitized by these wasps typically have a swollen, balloon-like appearance and turn brown or black. These parasitized aphids are called “mummies.” Other braconid wasp species spin conspicuous pupal cocoons after emerging from a host. 

CSU Extension Fact Sheet

Download or view the CSU Extension’s PDF fact sheet for your reference.