Ichneumonidae is a family within the insect Order Hymenoptera. Insects in this family are commonly called ichneumon flies, ichneumon wasps, or simply ichneumons. Ichneumon wasps are important parasitoids of other insects. Common hosts are larvae and pupae of Coleoptera, Hymenoptera, and Lepidoptera. There are approximately 3,000 species in North America - more than any other Hymenoptera family. They differ from the wasps that sting (Scolioidea, Vespoidea and Sphecoidea) in that the antennae are longer, usually with 16 or more segments. Female ichneumons frequently exhibit an ovipositor longer than their body. Ovipositors and stingers are homologous structures; some Ichneumons inject venom along with the egg, but they do not use the ovipositor as a stinger, per se. Stingers are used exclusively for defense; they cannot be used as egg-laying equipment. Males wasps do not sport stingers or ovipositors. In the genus Rhyssa,Ichneumon wasps of both sexes will wander over the surface of logs, tree trunks, and even grass stems tapping with their antennae. Each sex does so for a different reason; females are 'listening' for wood boring larvae of the horntail wasps (hymenopteran family Siricidae) upon which to lay eggs, males are listening for newly emerging females with which to mate. Upon sensing the vibrations emitted by such a wood-boring insect larvae, the female wasp will drill her ovipositor into the substrate until it reaches the cavity wherein lies the larva. She then injects an egg through the hollow tube into the poor unfortunate's home. There the egg will hatch and the resulting larva will devour its host before emergence. Some species of ichneumon wasps lay their eggs in the ground, some even inject them directly into a host's body. How the female wasp is able to drill with her ovipositor into solid wood is still somewhat of a mystery to science, though it has been found that there is metal (ionized manganese or zinc) in the extreme tip of some species' ovipositors.