An ichneumon wasp, Megarhyssa macrurus (Linnaeus) (Hymenoptera: Ichneumonidae). Photo by Drees.
Common Name: Ichneumon wasp
Scientific Name: Varies
Order: Hymenoptera
Description: Adults of Megarhyssa macrurus lunator have brown bodies, up to 1 ½ in length, marked with black and yellow markings and transparent wings. Females have a very long (up to 3 inches long) thread-like egg-laying structure (ovipositor) on the end of their abdomens.
Megarhyssa macrurus macrurus (Linnaeus) is similar in size to M. m. lunator, but the body and wings are dark brown. Rhyssella species are black with white markings, not as large as Megarhyssa, and parasitize wood boring woodwasp larvae (Xiphydriidae) in conifers. Possibly a more common ichneumon is Ophion nigrovarius Provancher, which is reddish or dark yellow-brown, 1-inch long, with brown-tinted wings. Larvae feed on immature stages of white grubs (Coleoptera: Scarabaeidae). Adults can sting and are frequently encountered around lights in and around the home. Most ichneumons are smaller parasitic wasps. Adults often feed on body juices of hosts and larvae feed in on immature stages, such as larvae and pupae of butterflies and moths (Lepidoptera), beetles (Coleoptera), flies (Diptera), and sawflies and wasps (Hymenoptera). Some species attack spiders or are hyperparasites (parasites that feed on other parasites) and, thus, might not be considered to be beneficial insects. Most species overwinter in the cocoon as a mature larva, although some spend the winter as adult females. There may be one to 10 generations produced annually depending on the species.
An ichnuemon wasp, Enicospilus sp.,(Hymenoptera: Ichneumonidae: Ophioninae), parasitic on Lepidoptera larvae. Photo by Drees.
Life Cycle: The larva of M. m. lunator hatch from eggs inserted into the tunnels of the pigeon tremex. Larvae are grub-like and develop through several stages (instars) before pupating inside a cocoon in host insect tunnels. Adults emerge in the spring.
Habitat, Food Source(s), Damage: Mouthparts are for chewing. Females of M. m. lunator insert their ovipositor through the bark of dead deciduous trees and lay eggs in the tunnels of the pigeon tremex, Tremex columba (Linnaeus) (Hymenoptera: Siricidae). Larvae crawl along the tunnel until encountering a host larvae on which they feed. Adult wasps can occasionally be found in the spring (March), attached to the trunk on a dead tree with their long ovipositor.
Pest Status: The family, Ichneumonidae, contains many species considered to be beneficial insects because their larvae develop on other insect pests; although generally considered to be harmless some species are capable of stinging when improperly handled.
Management: None, beneficial insect.
For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.
Literature: Arnett 1985; Borror et al. 1976; Metcalf et al. 1962; Swan & Papp 1972.