noun
: any of a large superfamily (Ichneumonoidea) of hymenopterous insects that have many-jointed antennae, fore wings with a usually triangular stigma, petiolate abdomen, and in the female a commonly long sheathed ovipositor for use on other insect larvae (as caterpillars) which the larval ichneumon fly burrows in and feeds on and ultimately kills thereby constituting an important natural check on many destructive insects