''Megarhyssa nortoni'', also known as Norton's giant ichneumonid wasp or the western giant ichneumonid wasp, is a species of large

ichneumon wasp The Ichneumonidae, also known as ichneumon wasps, ichneumonid wasps, ichneumonids, or Darwin wasps, are a family of parasitoid wasps of the insect order Hymenoptera. They are one of the most diverse groups within the Hymenoptera with roughly 25, ...

Subspecies

There are two described

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

of ''Megarhyssa nortoni'': *''M. nortoni nortoni'' (Cresson, 1864) (western US and southwestern Canada) *''M. nortoni quebecensis'' (Provancher, 1873) (northeastern US and southeastern Canada)

Description and identification

''Megarhyssa nortoni'' is black, reddish brown, and yellow and has distinguishing round yellow spots down the side of the abdomen. Its legs are mostly yellow. Its wings are transparent, and the body is elongated with a length of . The female is notable for an

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typica ...

of to in length. The male is less colorful with no ovipositor.

Distribution and habitat

Western Giant Ichneumon Wasp imported from iNaturalist photo 302983876 on 2 November 2023

This species is native to North America including parts of the United States and Canada. The subspecies ''M. nortoni nortoni'' has a western distribution from the Pacific Coast to Colorado while the subspecies ''M. nortoni quebecensis'' has an eastern distribution from the northeastern US and southeastern Canada. It is found in coniferous forests where

horntail Horntails or wood wasps are any of the 150 non-social species of the hymenopteran family Siricidae, a type of xylophagous, wood-eating sawfly. The common name "horntail" derives from the stout, spine-like structure at the end of the adult's abdom ...

larvae are present. It has also been introduced to Australia, New Zealand, Tasmania, Brazil, and South Africa to help control horntail forest pests.

Behavior

''Megarhyssa nortoni'' is a predatory insect. Its larvae are parasitoids of

wasp larvae in coniferous trees. The adult female hunts horntail larvae for egg placement. It smells wood-eating fungus, utilized by the horntail larvae to predigest wood pulp, and uses its antennae to detect vibrations made by the horntail larvae. The female ''M. nortoni'' curls its ovipositor over its abdomen to insert the tip of the ovipositor at a right angle into the bark and cuts into the tree until it reaches the horntail larval tunnel. The female then deposits a very slender egg through its ovipositor into the tunnel on or near the horntail larva. The ''M. nortoni'' larva then hatches to eat the live horntail larval host from the inside causing the horntail larva's eventual death. The ''M. nortoni'' larva pupates inside its host and emerges the following summer as an adult. Although imposing, the female ''M. nortoni'' does not sting and is harmless to humans. Adult ''M. nortoni'' feed on nectar and water.

References

{{Taxonbar, from=Q6808837 Ichneumonidae Insects described in 1864 Taxa named by Ezra Townsend Cresson Insects of Canada Insects of the United States