Megarhyssa is a type of parasitic wasp belonging to the family Ichneumonidae. It is known for its long, slender body, reaching up to 4 inches in length. The female Megarhyssa has a distinctive ovipositor, which can be as long as its body, used to inject eggs into the wood of trees infested by wood-boring larvae. The larvae of Megarhyssa then feed on the larvae of the wood-boring insects, ultimately killing them.