Monday, August 25, 2014

Doorstep gift, unwrapped.

Last month, I posted the photo of a cocoon that I found on my doormat one morning.

Wooly bear caterpillar cocoon, found July 6th.

I put it in a plastic container with a perforated lid, and left it outside, near the door where the caterpillar had chosen to sleep. I made sure to check it every day.

24 days later, July 27th, something was fluttering around inside the container. But it was not the expected moth.

Not a moth.

BugGuide identifies it as a Braconid wasp, in the genus Macrocentrus. These are parasitoids; parasitic animals that inevitably kill their host. The female wasp lays an egg in a larva of her preferred species. The egg hatches and the wasp larva grows inside the caterpillar until it (the caterpillar) pupates. Then the larva of the wasp begins to feed off the host's body, pupates inside the dead caterpillar's cocoon, and finally emerges as an adult, ready to mate and find itself another caterpillar to start the cycle again.

Exit hole.

Face view. I'm not sure how that extra insect leg got in there.

Pretty stained-glass wing.

Dried out and warmed up, ready for take-off. Work to do!

This wasp is a female; the spike at the end of her abdomen is the ovipositor, the egg-laying tool. She's got about a week to find herself a mate and a moth larva before she dies.

Some species of these wasps are used as pest control, to kill the caterpillars and other larvae that damage our crops. And wasps though they are, they don't sting humans.


  1. amazing thanks so much for sharing this!!!

    I wonder if the wasp is a generalist or if they like specific species to prey on. I imagine tomato farmers would love some help with the crawlies that like tomato plants.

  2. What I find amazing is all the critters that we would never see, what with their adult form being observable for mere days. Thanks for hatching this one out for us!

  3. What an interesting surprise!

    Great photography.


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