The name comes from Greek: ichneuein = to hunt out or hunt up.

The family of the so-called parasitic wasps (e.g., Ichneumon nigritarius) represents the biggest group among the Hymenoptera and among the so-called  parasitoids, which also include species from other insect groups. The European wood wasp Rhyssa persuasoria reaches a body length of up to 5 cm and has a similarly sized ovipositor, by the help of which it injects its eggs into larvae of butterflies (Lepidoptera), beetles (Coleoptera), or even eggs of spiders (Arachnida). Since these ichneumonids mostly kill their hosts, they are called  parasitoids, since the interest of “true parasites” must be to keep alive their hosts, since they have no more a free-living stage.