Tent Caterpillars Are Back

There is no chance of escaping the hungry little pests, even if you squish as many as you can catch.  The tent caterpillars are here and have already eaten their way through thousands of poplar tops, most noticeably in the Rycroft area.

The following post was written last June, when the Peace Country was well into the caterpillar siege.  Pictures are by Carolyn Brown.  You can also find more fascinating information about tent caterpillars here.

If you’ve been in the valley in the last couple of weeks, you could hardly have missed the bare aspen trees and the smushed caterpillars all over the highway.  You were probably grossed out.

Now, have you ever been in the forest and heard what sounds like rain falling all around you… except the sky is blue and there are no raindrops?  That’s the caterpillars, of course.  No, not millions of caterpillars munching.  It’s millions of caterpillars pooping.  The leaves they eat are only about half digestible, so the little pests are dropping fecal pellets all the time.  Now that’s leaf litter.  You are grossed out.


Wikipedia is a bit off-hand about these hungry little beasts:

They are often considered pests due to their habit of defoliating trees. They are among the most social of all caterpillars and exhibit many noteworthy behaviors.

It’s true that they are interesting.  Tent caterpillars must eat young leaves, so they have to go around eating as much as they possibly can before the leaved become too aged.  A mass of them can actually eat themselves into starvation if they run out of new leaves.

Each time they head out to feed, several times a day, the caterpillars all leave their special P1000127little tents.  Each tent is placed so that the morning sun will shine on it.  In order to digest all those leaves, the caterpillar’s body temperature must be over 15 °C.  That means the tent has to catch the heat and hold it.  It is constructed of separate layers of silk with spaces between.  Each space is a different temperature, so the caterpillar can choose the most comfortable “room”.  The tent may be 30° higher than the outside temperature (so these cold, rainy nights aren’t going to kill them).  Once finished feeding, all the caterpillars return to the tent.  For a nap?

Tent caterpillars have development cycles of decades or more.  They pick a little for a couple of years, and then devour the entree over two to three years.  That’s called “outbreak mode”.  Anyone know what year we’re on?

In 2002-3, tent caterpillars stripped 7.5 million acres of trees in Minnesota.

However, the leaves generally grow back by the beginning of July.  The gap in the aspen canopy also gives other tree species a chance to grow.  Although the caterpillars may make your skin crawl and they are detrimental to the beauty of the valley, they don’t wreak absolute destruction.  Wait a few weeks and we’ll have forgotten they were here.

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