A massive parasitoid wasp with an astonishingly long ovipositor (up to 4 inches). Females drill through bark and wood to lay eggs in pigeon horntail larvae living inside dead trees.

Also called: Giant Ichneumon, American Pelecinid

Native status: Native to eastern North America

§ Quick facts

SizeBody 3–4 cm; ovipositor up to 10 cm in females
Weight~1 g
LifespanAdults 2–4 weeks
OrderHymenoptera
FamilyIchneumonidae

§ Encyclopedia

Megarhyssa macrurus, also known as the long-tailed giant ichneumonid wasp or long-tailed giant ichneumon wasp, is a species of large ichneumon wasp. It is a parasitoid, notable for its extremely long ovipositor which it uses to deposit an egg into a tunnel in dead wood bored by its host, the larva of a similarly large species of horntail.

Source: Wikipedia — Megarhyssa macrurus Licensed under CC BY-SA 4.0

§ Identification

Field marks. Long slender black wasp with yellow body markings; females have extraordinarily long thread-like ovipositor extending behind body; long antennae.

Similar species. Other Ichneumon species (many; expert ID). Pelecinus polyturator (similarly long ovipositor; different family). Horntail wasps (host species; thicker body).

Voice. N/A

§ Diet & behavior

Diet. Adults feed on nectar. Larvae are internal parasites of horntail wasp larvae developing inside dead wood.

Behavior. Among the most spectacular wasps in North America. Females have extraordinarily long ovipositors (the "stinger") that look terrifying but are completely harmless to humans — they cannot sting. Instead, females use the ovipositor to drill through tree bark up to 10 cm thick to deposit eggs into the burrows of pigeon horntail wasp larvae, which become living food sources for the ichneumon larvae. The drilling can take 30+ minutes and may be aided by vibration-based detection of host larvae.

§ Range

Eastern US

§ Habitat

Mature forests with deadwood

§ Threats

Forest fragmentation, removal of dead wood.

§ Conservation status

According to the IUCN Red List, the giant ichneumon wasp is currently classified as Least Concern.

§ What helps

Leave dead trees standing where safe. Don't fear ichneumon wasps (they cannot sting).

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§ Further reading

§ Sources cited

  • BugGuide
  • American Entomological Society
  • iNaturalist