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A good year for caterpillars?


Are caterpillars having a good year?

John and Anita Randle have been reading this column for years. I often get an email from John and generally there’s a perplexing question at the heart of it.

Recently John wrote, “Is there an unusually high number of caterpillars this spring? I can’t even walk through the grass without it sounding like ‘pop, pop, pop.’

“Could we be in a cycle like we had last year with the cicadas?

“I do not have a large number of tent caterpillars in my trees, but what I do have are too high to deal with.”

I have had many tent caterpillars trundling about my place, on the ground and elsewhere. But is it more than last year, or 10 years ago?

I’m not sure. I didn’t take a census in years past.

Without any hard caterpillar population data, I cannot really answer John’s question but I can speculate.

As odd as it sounds, this could be a product of global warming.

Many moths and butterflies lay their eggs in the trees so that when the young caterpillars hatch, they have leaves to eat.

Traditionally April is timed so that the caterpillars emerge as the leaves unfold, thus the little fuzzy things have plenty of food.

And to keep the caterpillar population in check, the migrating birds return about the same time.

Most of the caterpillars are eaten with just enough surviving to metamorphose into adult moths and butterflies to repeat the process. It’s nature’s balance.

But, things are getting out of sync. Climate change has led to the leaves and caterpillars appearing earlier each year. Their emergence is temperature related.

Data collected by satellites that measure when the land “greens up” in North America reveals that spring has been arriving eight hours earlier every year since 1982.

That’s almost nine days in 26 years. Bird migration operates a bit differently.

Their migration is triggered by the number of hours of daylight, or day length. And the length of days has not changed.

The big wave of migrating birds is just now beginning to arrive.

The caterpillars, perhaps taking advantage of a head start, are already leaving the trees and hiding somewhere near the ground where the canopy birds — warblers, vireos, cuckoos – do not venture.

That’s my speculation.

If I’m right, more of the caterpillars will survive, which could yield an abundance of moths and butterflies. Also, the returning birds may not find enough food to fatten up sufficiently and will produce smaller clutches.

Time will tell.

Thanks, John.





Lyn Bales can be reached at 865-577-4717, ext. 19 or stephenlynbales@gmail.com. His book “Natural Histories: Stories from the Tennessee Valley” is available at local bookstores.

 

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