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A Closer Look: The Great Ichneumon

By

Chris Grondahl

GIF - Female Ichneumon (PIC)

Originally published in:
North Dakota Outdoors
(August, 1997)


Official Publication of the
State Game and Fish Department
100 North Bismarck Expressway
Bismarck, North Dakota 58501-5095


This resource is based on the following source:
Grondahl, Chris.  1997.  A closer look: The great Ichneumon.  North Dakota 
     Outdoors 60(2):18.
This resource should be cited as:
Grondahl, Chris.  1997.  A closer look: The great Ichneumon.  North Dakota 
     Outdoors 60(2):18.  Jamestown, ND: Northern Prairie Wildlife Research Center 
     Online.  http://www.npwrc.usgs.gov/resource/wildlife/closlook/ichneumn.htm  
     (Version 15MAY98).

Return to A Closer Look Series
"Ick" is probably the first term that comes to mind after seeing a member of the family Ichneumonidae. These insects are from a large family of wasps that vary greatly in size and color. Most are brown or black with yellow or white markings, and measure up to three inches in length.

In many species the abdomen is long and slender, becoming thicker at the tip. In females, this tip often ends in a trailing, threadlike ovipositor for laying eggs. Most females do not sting. Adults may not eat, but drink water and nectar from plants. They live throughout North America in deciduous and mixed forests with dead and dying trees.

Ichneumons are unique because they are parasitic. Ichneumon larvae feed on other insects and spiders, helping to control insect populations.

GIF - Three female Ichneumons (PIC)
Above: Two Ichneumon females line up on a tree as if in a procession of reproduction. Various species of the family Ichneumonidae exist across the woodland habitat of North America. This species is the western giant Ichneumon characterized by its black body, yellow and red spots and mostly yellow legs.
Inset: A close-up view of a giant female Ichneumon shows the long, dark ovipositor boring into tree bark. After the egg is deposited into the larval tunnel of another tree-boring insect, the Ichneumon larva develops by feeding upon this host larva.

That larval Ichneumon can prey upon other insects is possible because of the method by which the adult female lays its eggs. Mated adult females fly from tree to tree, pressing their long antennae against bark to detect vibrations made by insect larvae. Having found life underneath the bark, she curls her ovipositor up over her abdomen, then curves it down to enter the bark at a right angle. The sharp tip cuts into the bark until it reaches the larval insect tunnel. An Ichneumon egg is then inserted into the tunnel, where it will hatch and feed upon the host larvae until it develops into a mature larvae itself.


Chris Grondahl is a biologist with the Deparment's natural resources division.

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