Numbers
Over 3100 species in North America.
Identification
Slender, wasplike. Two recurrent veins. 2nd submarginal cell small or lacking. Base of cubital vein lacking, 1st submarginal and 1st discoidal cells fused. 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.
Habitat
They are common insects, found almost everywhere.
Food
The larvae feed on a great variety of hosts, though most species attack only a few types of hosts; some ichneumons attack spiders. Most are internal parasites of the inmature stages of the host.
Remarks
One of the largest families of insects with over 3100 species in North America (60,000 worldwide). The majority resemble slender wasps. They differ from the wasps that sting (Scolioidea, Vespoidea and Sphecoidea) in that they have the antennae longer and with more segments usually 16 or more). In many ichneumons the ovipositor is quite long, often longer than the body.
It is divided into 24 or 35 subfamilies depending on different authors..
Many Ichneumons are of value in the control of noxious insects.
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.
Internet References
Ohio State University, brief description of all subfamilies. Also at same site is a classification down to the level of genus for all species worldwide
Cedar Creek Guide to subfamilies.
