Wednesday, April 20, 2011

Wasp Wednesday: Colpotrochia

Prowling around outdoor lights at night to look for insects can be fraught with difficulty, especially in a small town. The first time I went out to investigate the lights of South Deerfield, Massachusetts, I was confronted by the local constabulary. Hey, can I help it if the best-lit buildings are banks and the U.S. Post Office? I cleared a background check and was rewarded in the long run by encounters with many six-legged personalities, including this ichneumon wasp in the genus Colpotrochia on June 23, 2009. Oh, by the way, I found it by the lights on the police station.

The genus Colpotrochia is placed in the subfamily Metopiinae, the members of which all lay eggs in the host larva, emerging as adult wasps from the host pupa. According to the Database of Hymenoptera in America North of Mexico there are four North American species in the genus, all ranging from the Atlantic coast to barely west of the Mississippi River. Two of those are known in Massachusetts: C. crassipes and C. trifasciata. These are not very large insects, averaging between six and ten millimeters in body length.

Gardeners will be delighted to learn that the female wasps use their very short ovipositor to lay eggs in caterpillars, especially leafrollers in the family Tortricidae. The wasp grub that hatches inside the caterpillar slowly consumes its host, avoiding disruption of the caterpillar’s life cycle until after it pupates. Instead of a moth emerging from the pupa, out comes a wasp.

Those interested in identifying ichneumons to the subfamily level (no mean feat) might start with this PDF file, an Identification Key to the Subfamilies of Ichneumonidae, by Gavin Broad. It provides a very good start for learning how to tell ichneumons from braconids, and other basic information, all well-illustrated.

Special thanks goes to Bob Carlson for identifying my image after I posted it to BugGuide.


  1. Too funny Eric, reminds me of our trip to the Smoky Mountains, we stayed in a cabin right outside of a small town called Townsend, TN. I coerced Joey into driving into "town" so I could hunt bugs by the lights. The local sheriff pulled in behind us at the nature and information center. I like you......couldn't help that it was the best lit building in the entire town. After explaining what I was doing, the officer looked at me like I had taken leave of my senses....then I completely embarrassed Joey by asking the sheriff if he knew of any good places to hunt bugs....I just had to ask....LOL
    This is a beautiful ichneumon wasp. Thanks for the info and the PDF file. Great info.

  2. Interesting as always and thanks for the link!

  3. I haven't had that experience but my late husband found himself in serious trouble once when collecting frogs in South America. He accidentally crossed the contested border between Ecuador and Peru --just a decrepit barbed wire fence-- and found himself facing the guns of the Peruvian border patrol. It took several hours to get out of that mess.


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