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Eastern Tent Caterpillars

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After ten years of living in the Eastern Sierra, I’ve begun to notice year after year an interesting cycle in nature found on all the sage brush we have through the Mammoth Lakes area and the entire Eastern Sierra for that matter.  Each spring, a significant amount of the sage brush that covers our lands seems to be occupied by numerous spider web-like growths.  Within each of those webs are thousands of little black dots (eggs) that soon hatch into a black and orange caterpillar.

Eastern Sierra Caterpillar


Well after walking my dogs this week along one of Mammoth’s paved paths from Mammoth Creek Park to that lookout that looks down on Lake Crowley, I couldn’t help but notice all the hatchings of these caterpillars.  So I snapped the above photo and came home to start researching what type of caterpillars these are and what type of flying insect they will eventually become.


These creatures are named the Eastern Tent Caterpillars (or Malacosoma americanum for those of you who want to sound really smart), most likely because the silk webs they hatch in are often times referred to as tents.  The tent of these species is among the largest built by any tent caterpillar.  At the beginning of the cycle, the adult moth lays her eggs in one single batch during these spring months.  That batch contains on average 200-300 eggs and hatches within about three weeks.


I’ve been able to research enough to identify that these caterpillars’ eggs are laid by female moths, and of course soon hatch into moths, but I’ve been unsuccessful in identifying which species of moths they are.  If anyone knows, please chime in!  The below picture reminds me of what is about to cover my windshield the next time I drive north or south on Hwy 395.  But then I thought that maybe these tent caterpillars are the Pandora moths that seem to migrate to the Mammoth lakes Post Office every season, as us locals get an annual reminder of the movie The Silence of the Lambs.  I’ll be sure to snap a photo this year and share that annual odd occurrence with all you non-locals to show you what I’m talking about. It’s kind of creepy.


Written by Eric Leach

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