A particularly nasty variety of insect.
Ichneumons parasitize most insect groups - especially moths and butterflies and other Hymenoptera, as well as spiders.
The females lay their eggs in or on the larvae or pupae (rarely eggs or adults) of the host. The ichneumon larva feeds on the fats and body fluids of the host until fully grown, then usually spins a silken cocoon. The species that parasitise hosts in open habitats usually develop as internal parasites; those that attack hosts in concealed places, such as wood burrows, usually feed on the host externally. In most cases a single larva develops in one host; in some cases, however, many larvae develop in a single host.
It is difficult to imagine a good or beneficient God designing such a means of reproduction, where life is brought forth by the literal eating alive of another living entity. Such a design may be efficient, but it is by no means beneficient.