Mystery critter at the UT Arboretum

When I went into the office at the arboretum today, Lynn (the secretary) said, "I'm glad you are here, Yvonne (a staff member) found a strange bug we want you to look at!" It was in an empty margerine bowl in the director's office. When I opened the lid I was amazed at what I saw!


Whatever the thing was, it had curled into a tight ball! It looked like part armadillo, part millipede! I was leery to touch it, I didn't know if it would bite. When she told me it had legs at just the front near the head I figured it had to be an insect of some sort. After observing it in Lynn's office for a few minutes and it staying curled up, I decided to take it outside and put it in the sun to see if it would open. That did the trick! It slowly began to move and I was surprised to see how big it was. It turned out to be ~3" long! I finally decided that it was some kind of beetle larva.


After spending a few minutes on Bugguide.net, Lynn found out it is a Giant Glowworm larva. I had to laugh when I saw that many of the other photos of this larva were taken in a cup or some other container too! When I tried to photograph it on the ground, it immediately tried to bury into the soil. Its favorite food is millipedes! With the bright coloration it has, I wouldn't be surprised if it was poisonous. I was interested to learn that the females are bioluminescent, they produce light as a deterrent to nocturnal predators. They are also called "Railroad Worms" and are in the family Phengodidae of the order Coleoptera.

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Sometimes truth is stranger than fiction!

I got a call from my neighbor, Jason, who lives behind me (he's also the one who found the Ichneumon wasp a couple of weeks ago). When I walked in the back yard his son, Isaac, said excitedly, "It's a caterpillar with eggs on its back!" I asked if it was on their tomato plants; when they said "yes" I knew immediately what they had.

A Parasitized Tomato Horn Worm
(click on photo to enlarge)

It was a Tomato Horn Worm (Manduca quinquemaculata), a sphinx moth caterpillar that had been parasitized by a small braconid wasp. The wasp had laid her eggs inside the caterpillar several weeks ago. The larvae hatched and began to eat the caterpillar alive. When they were finished eating, they tunneled outside the caterpillar and spun these white coccoons on its back. Soon the wasps will mature, chew their way out of the cocoons and start the cycle all over again. The tiny wasps are a good form of natural pest control. So, if you find a caterpillar that has cocoons like this in your garden, leave it alone and let nature take its course.

The 8 small yellow and orange dots on the sides of the caterpillar's abdomen are the spiracles, the holes used for breathing. The species name quinquemaculata means "5 spots". Caterpillars do not have compound eyes like adult insects, they have simple eyes (these small eyes can be seen on the head if you enlarge photo by clicking on it). The simple eyes can just detect light and dark.