Megarhyssa macrurus (Ichneumonidae), a parasitoid, ovipositing into its host through the wood of a tree. The body of a female is c. Lua error in Module:Convert at line 1850: attempt to index local 'en_value' (a nil value). long, with an ovipositor c. 4 inches (100 mm) long.

Braconid wasp Aleiodes indiscretus laying eggs in a caterpillar

Braconid parasitoid wasp Apanteles cocoons on a caterpillar

By far the greater number of wasps (over 500,000 species in the superfamily Chalcidoidea alone) are a special type of parasite. They are parasitoids which lay their eggs in or on the bodies of other insect species (usually the larvae such as caterpillars).

Different species specialise in hosts from different insect orders, most often Lepidoptera, though some select beetles, flies, or bugs; the spider wasps (Pompilidae) exclusively attack spiders.