Tent caterpillars and sleeping bag moths

Ok, so there are no sleeping bag moths (that I’m aware of), but there are tent caterpillars.  I first came across these animals in the middle of Missouri.   While walking around in the woods, there, we used to see so many tents that some of the trees were just completely covered with (and almost completely defoliated by) these silken things.  They appeared to be more of a problem for some species of trees than others.  In the past week or two, I’ve started to see these tents forming around here, as well.

Take a walk on the greenway along Little Sugar Creek at Freedom Park and you’ll see a number of the tents forming in the trees.  In fact, if you look closely, you may also see the actual caterpillars walking around feeding, as well.  These tents have a number of functions:  protection from predators, gathering place, lounge and happy hour bar.  The caterpillars will leave the tent to forage, but head back at various times of the day to rest and digest in the tent.  Apparently there is a particular timing to their activity patterns, with peaks in the morning, the middle of the afternoon and just after sunset.

Fitzgerald, T.D., T. Casey and B. Joos.  1988. Daily foraging schedule of the field colonies of the eastern tent caterpillar Malacosoma americanum. Oecologia 76:  574-578.

I was in the park right around 2:30 the other day, which is when I spotted a huge number of them walking around on a brick wall on the greenway.  I poked at the caterpillars for a bit and watched them follow each other across the wall without really thinking about them at the time.  They were a short distraction for me while I was doing other things in the park.  Now, after looking up some stuff about them, I realize that I should have paid more attention.  I knew that they built the large, silken tents in the trees.  I knew that they hung around in large groups in the tents and I knew that they ate a lot of plant material.  What I didn’t realize about them is that these little caterpillars are highly social.  Not only do they live together in these tents, but they also mark trails that allow other individuals to find good sources of food.  Their signals are quite specific, too!  The trail that is left by a caterpillar who feeds is different from that left by one who doesn’t feed.

Fitzgerald, T.D.  1976.  Trail marking by larvae of the eastern tent caterpillar. Science 194 (4268):  961-963.

Additionally, the caterpillars can leave messages that are even more specific.  For instance, caterpillars that feed on young leaves of preferred plants recruit more individuals to the site than caterpillars that feed on older leaves or on young leaves of less preferred plants.  They also recruit more individuals to sites with less competition!

Fitzgerald, T.D. and S.C. Peterson.  1983.  Elective recruitment by the eastern tent caterpillar (Malacosoma americanum). Animal Behaviour 31:  417-423

The chemical signals that they leave are quite important, then.  They may just be a gradation of excitement (‘I ate, but it was just so-so’ compared to ‘wow! that was a good meal’) or they may contain more specific kinds of information, too.  Either way, a lot of information is produced and perceived in the signals that these caterpillars use.  It’d be like me leaving a little mark on the floor that said, “go to the Harris-Teeter now.  No one is there and the tomatoes are in season.”  Of course, I can say it (or type it), but I can’t leave it in scent trail for you to find later (when I’m not around).  Chemical communication is impressive in that way.  The signals that the animals produce stick around long after the animal has passed that spot (or returned to the tent to take a well-deserved nap).

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About thomasbiology

I'm an Associate Professor of Biology at Queens University of Charlotte with a background in animal behavior with an emphasis in bird song. I've got two secret goals with this blog (well, since I'm sharing them, they're not so secret): 1. To encourage people to look at the natural world around them- not just as a hiking destination, but to notice all the little things moving around them all the time; and 2. To show some of the science that relates to these little things moving around. There's some really fascinating research out there that so few people get to see.
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