Wednesday, August 1, 2012

Ichneumon Wasp

During most of the year, no matter where you are, there are insects quietly going about their business.  Unless they bite or are large enough to intrude upon our senses, they go unnoticed.  I try to take the time to observe some of these tiny wonders and have strained my eyes attempting to see some small, but fascinating creatures.  Occasionally, the fantastic arrives in a larger package. 

This is a female Ichneumon Wasp.  I believe this is Megarhyssa greenei, but I don’t have any reference that identifies all of the know species of this genus, so I don’t know if there are any look-alike species that could complicate the identification.  Regardless of the species, this genus has a remarkable life history.  The larva of this wasp begins life feeding on the inside of a Wood Wasp larva boring its way through the deep wood of a tree.  The female Ichneumon Wasp plants the egg by way of a long egg laying apparatus, AKA ovipositor.  That tail-like projection is the sheath that protects the ovipositor.  The sheath peels back as the ovipositor penetrates the wood.  The egg is actually larger in diameter than the ovipositor and squeezes through in an elongated shape that reforms into a more typical egg shape once it reaches the target.

I met my first female Ichneumon Wasp when it landed on the bread basket in the center of the table at our annual family picnic.  I was ten years old at the time.  I was never around anyone who had any interest or knowledge of natural history, so my knowledge came from a few books I was able to acquire along with speculation and a highly developed imagination.  The other dozen or so people at my table began to take notice when I pushed my food aside and did a sort of belly slide in the direction of the bread basket.  Someone was revving up to unleash a little discipline when I shouted something like “Man, look at the size of that stinger.”  Discipline was forgotten as everyone scrambled to get untangled from the attached bench seats and put distance between themselves and the wasp.  I later learned that the ovipositor did not function as a stinger and was no cause for alarm.

The hosts for the Ichneumon Wasp larvae are most often found in ailing or recently dead trees.  I’m not sure how the female senses the larvae of the Wood Wasp.  I watched for about ten minutes, thinking that the wasp might begin hunting on one of these recently fallen trees, but she eventually just took off and kept on going.

Bright colors often serve as a warning that an insect is dangerous and ought to be left alone.  Bright orange and yellow certainly stands out on green foliage or brown tree bark.  She may be defenseless, but anything that avoids wasps would certainly stay away from this lady.


  1. Fascinating creature! I remember seeing one and thinking it looked particularly dangerous.

  2. Hi Pat. It does look like it could inflict quite a bit of pain.