Western Tent Caterpillars






This is a different topic for me, but I had to write about the infestation we’re having.  Tent caterpillars, or  Malacosoma californicum  as they are known scientifically, eat the leaves of our 80-foot-alders, crawl over any available surface, and poop everywhere.  Looking up, I see bare branches and a few lacy leaves.  Looking around me on decks and vehicles and furniture, I see fuzzy, brown, creepy caterpillars and thousands of sticky black spots – their feces.

Every few hours I make the rounds, spraying with the soap that’s safe for all the lovely plants and animals in our island paradise.  But my spray bottle and I are no match for the little eating machines.

When will this plague end?



About treewithroots

Magda and Brent solve crimes and unravel mysteries on Mayne island. These exciting mystery/adventure stories for 9 - 13 year-olds, Magda's Mayne Island Mystery, Mayne Island Aliens and Mayne Island Skeletons, are available at various bookstores in the Gulf Islands. Amber enjoys reading to school classes. Teachers, please contact her if you'd like her to read to your class.

5 responses »

  1. I understand that the tent caterpillars have cycles that may span years of ups and downs in population. On Mayne it sounds like you are on an up whereas here in Victoria we seem to be on a down, at least in our backyard. We have had to remove a few nests from our apple tree and the neighbours overhanging and seriously sick cherry but nothing like some years.

    I do wonder what the tent caterpillars natural enemies might be a funghi, larvae or perhaps a particular bird and what part we humans have played in upsetting this balance in this part of the world. Have yet to do the research!

    I heard an interesting argument about unwanted species recently – in a nutshell, a weed or an unpleasant caterpillar is in the eye of the beholder – the rest of nature doesn’t give a damn. If a weed, introduced plant or an insect thrives it may be just what is needed in the long run, for example in the soil (caterpillar poop for compost!). Time means nothing to all but one of earth’s species. The natural environment is constantly changing on a scale and on timeline we can barely fathom whether we humans like it or not. I think I have paraphrased Richard Walker, food forester.

    • “Time means nothing to all but one of earth’s species.” True, Denise. I’ll try to take that perspective. We’re so aware of time, to a degree that is harmful, I think.

    • Hi. Well, I did my research, and it looks like help is at hand, from its natural enemy, the tachinid fly. Here’s what I found.

      Parasitic flies, in the family Tachinidae, are sneaking up behind unwary caterpillars and slapping them in the back of the head with one of their kids! Pictured is a great photo from Washington State Department of Agriculture chief entomologist, Eric LaGasa, showing the white egg of a tachinid fly located just behind the head of the tent caterpillar. Soon, this egg will hatch and a maggot will crawl out to gain entrance inside the caterpillar. Once inside the caterpillar, the maggot will graze on the not-so-vital organs like reproductive organs and fat bodies. Tachinid flies, such as in the genus Gonia, will continue to devour their host when the caterpillar has decided to pupate. Often you will find the devoured or almost-dead pupae and the pleasantly plump tachinid fly pupae in the same cocoon of the tent caterpillar.


  2. While all is nature, we still can try to rule. Maybe lots and lots of cotton candy will ensnare these woe-begotten nits.

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