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Family Ichneumonidae - Ichneumon Wasps

Wasp - Therion morio Wasp - Banchus Ichneumon Wasp - Dusona small wasp - Gelis - female Hover fly parasite - Diplazon laetatorius - female Ichneumon Wasp - Trogus pennator Thing - Ophion - male Pimplinae? - Pimpla pedalis - female Megarhyssa sp. - Megarhyssa macrurus - female
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon ("Parasitica" (parasitic Apocrita))
Superfamily Ichneumonoidea (Braconids and Ichneumons)
Family Ichneumonidae (Ichneumon Wasps)
Synonyms and other taxonomic changes
The family was revised by Henry K. Townes in the 1960s and 1970s. Some of his names are no longer in use or have changed meaning, due to conflicts with the International Code of Zoological Nomenclature or to advances in taxonomy. Many earlier comments within BugGuide, and much old literature, used Townes' names & concepts, such as Gelinae (now Cryptinae) and Ephialtinae (now scattered within Pimplinae). See summary of the history of Townes' classification.

This site follows the classification of Wahl(1) and not Townes
~5,000 described spp. in almost 500 genera in the Nearctic Region, possibly 3,000 more undescribed(2); arguably, the largest animal family, with the estimated 60,000 species worldwide (up to 100,000, according to some estimates(3)).
3-40 mm
Slender, wasplike. Two recurrent veins. 2nd submarginal cell small or lacking. Base of cubital vein lacking, 1st submarginal and 1st discoidal cells fused. Resulting vein structure called "horse head" shape:

Antennae with 16 or more segments and usually at least half as long as body.
They vary greatly in size and color; many are uniformly colored, from yellowish to black and others are brightly patterned with black and brown or black and yellow; many have middle segments of antennae yellowish or whitish.
The majority resemble slender wasps but differ from the stinging wasps (Scolioidea, Vespoidea and Sphecoidea) in having longer antennae with more segments (usually at least 16). Many have long ovipositors, often longer than the body.
Ichneumonids are notoriously hard to identify: aside from the sheer number of species, there are numerous cases of distant relatives that appear almost identical. Any identification based solely on comparing images should be treated as suspect unless an expert has said there are no lookalikes for the species or group in question.

Diagram comparing recurrent vein(s) of Braconid and Ichneumonid wings (Washington State University).

Key to subfamilies and general description in(3)


Subfamily Hybrizontinae (=Paxylommatinae)

Common almost everywhere
a great variety of hosts (mostly immature stages) is used, though most species attack only a few host types; some infest spiders and other non-insect arthropods(4)(5)
Life Cycle
Many hibernate as adults, usually under loose bark of fallen trees(6)
Many species help control insect pest populations.

A few minor subfamilies(3) are not yet in the Guide:
Diacritinae (Holarctic; 3 genera worldwide, 2 spp. in 2 genera in NA)
Microleptinae (Holarctic; a single genus represented in NA by 2 spp.)
Phrudinae (worldwide except Australian; 13 genera worldwide, 4 represented in NA by 6 spp.)
Stilbopinae (Eurasia and the Americas; 24 spp. in 3 genera worldwide; represented in NA by Stilbops latibasis)
Internet References
List of Ichneumon wasps and their hosts (UF's Natural Area Teaching Lab)
Les Ichneumonides (info on European spp.)