Redbud Mummies

Hiking a trail at Valley Water Mill Park I came across a small redbud tree with two branches covered with the cases above, over 200 total.  They were fastened on dead and green leaves as well as on the stems.  Most had a hole where a previous occupant had exited but some were still intact.  It was obvious that what ever these had been they were quite gregarious.

Campoplegine - silk cocoon underneath

I sent photographs to Dr. Scott Shaw.  He has written extensively on parasitoid wasps and he quickly responded that it looked like a "campoplegine ichneumonid. That would be the case if you can see the parasitoid silk cocoon underneath. Rogadine braconids cause a complete mummy of the caterpillar (no silk cocoon visible)."  A side view confirmed that suspicion.

Identifying a host caterpillar was a vexing problem.  After several dead ends I searched for "gregarious caterpillars redbud" and eventually came up with four suspects, Redhumped caterpillar-Schizura concinna, White Flannel Moth-Norape ovina, Io moth-Automeris io and Yellownecked caterpillars-Datana ministra.  I started from the top and found this Redhumped caterpillar Bugguide link, a photograph with parasitized specimens identical to mine.

Redhumped cats - Tom Murray CC

RH Moth - Tom Murray CC

Redhumped caterpillars (RH) are colorful and actually pretty, that is if they aren't skeletonizing your redbud leaves in mass.  They feast on a wide variety of woody plants and when they gang up on a leaf they are easy pickings for a parasitoid wasp depositing one egg per customer.  They will become a rather nondescript moth which has the cute habit of resting with its butt up in the air.

First instars - Edna Woodward

I was comparing the color and size of the RH cats and realized that these were parasitized at an early age.  The leaves hadn't been severely damaged and they were probably in the first instar when the wasp found them.  The literature suggests that a wasp can lay 100 eggs so this must have been a super fertile female or had a friend.

H. fugitivus - UC-IPM

Searching for parasitoids on Redhumps I came across this UC IPM publication listing two parasitic wasps attacking them, Hyposoter fugitivus, and Cotesia Schizurae.  This photograph of H. fugitivus from UC-IPM looks like a perfect fit.  I am waiting for confirmation.



I took several leaves home for study and after photographing them under the microscope I stored those without holes in separate containers. Two days later we announced the arrival of a bouncing baby wasp.  I watched it crawl around in its clear plastic box until I had to freeze it to photograph without it flying away.  Considering that over a hundred of its siblings had already emerged, I don't think this disrupted the cycle of nature.

Hyposoter lifecycle- UC-IPM

Life began for these wasps when their mother laid an egg in each of the small caterpillars.  As the larva emerges and starts to eat, the caterpillar continues to grow.  By the third or fourth instar it dies as the larva emerges and spins a cocoon to form a pupa.  This includes the flattened silk attachment to the leaf, tight enough that when I was pealing it away from the cocoon case it frequently brought some leaf with it.

When the male emerges, it will likely hang around to mate with emerging females, a steamy meeting described in this 1967 paper with the unromantic title of Sexual Behavior In Hyposoter fugitivus Hymenoptera Ichneumonidae.  The male touched the female's antennae, wiggling his alternating sides.  Then he started "vigorous wing fluttering" and.....we you know the rest and this is a family blog. 

A pair of these H. fugitivus and a few representative cocoon cases are in the mail, sealed in alcohol on their way for conformation and will become voucher specimens in the University of Wyoming Insect Museum, a long trip for a little wasp.

Special thanks to Dr. Scott Shaw for patiently sharing his knowledge this last week.  He is Professor of Entomology at the University of Wyoming, Insect Museum Curator and the author of Planet of the Bugs.


You will be interested to know that the presumed primary parasitoid, Hyposoter fugitivus (which caused the mummy), is known to have at least 12 different hyperparasitoids.  With a bit more research I was able to determine with high confidence that the 3 wasps you sent are Isodromas lycaenae(Howard), a cryptine ichneumonid known to hyperparasitize Hyposoter.  This is the wasp in your photos.  Nice catch.

This could be quite an interesting project for you and your students, if you can find more of the mummies.  With some patience, and by collecting many samples, you might rear 13 different wasps from the same caterpillar mummy!  You might be more likely to get the primary parasitoid, Hyposoter fugitivus, if you find solitary mummies.  The ones in groups, like you found, are far more likely to get hit by hypers.