Very Hungry Caterpillars

When we were camping at Mirror Lake State Park during the first week of June we came across an unusual occurrence. Caterpillars were everywhere. They were on the trees at the campsite, at the beach, on short hikes. They were all over. Also, all over were hunks of leaves which resulted from the very hungry caterpillars. This is a story some very hungry caterpillars. And, it is not the children's story by Eric Carle. 

The very hungry caterpillars I am talking about are now referred to as sponge moth caterpillars, and used to be known as gypsy moth caterpillars. One can guess why the name was changed. Sponge moths, then known as gypsy moths, first appeared in the state of Wisconsin in 1969. They can bare a trees vegetation, and from what I noticed they seemed to like oaks, but also were on other varieties as our campsite had few oaks. We were wondering why we kept seeing shards of leaves all over, even more prevalent than the caterpillars, and my wife made the connection.

Part of an eaten leaf on our chuck box

We were at the beach after a noon rainstorm, and a park worker was assessing condition of the picnic area and beach. My brother, using his phone, and AI, found the connection as gypsy moths, and I think that is the term that was used, not Sponge moths. We inquired of the park worker, and she said, yes they are gypsy moth caterpillars and we should kill them. My brother commented that it would take a high number of people to kill them there are so many. She noted that the prior week they had sprayed the park. 

Sponge moth caterpillar on a dish towel

The common spray for this caterpillar is a natural compound called Bacillus thuringiensis, commonly called Bt. It is found in the soil, and degrades within a week when exposed to sunlight. Now, I am not sure where all of these caterpillars were in the spray cycle, if they survived it, or were busy eating leaves coated with it that they would then perish. Essentially doing the task we were assigned by the park worker. 

They were so common, we found them crawling up the screen tent, between the tent window screens and the outer window (rain/wind) panel. I killed a few using my fingers, than thought the better of it, and resorted to placing them in the campfire, or smothering them with my shoe in the gravel/dirt surface of the campsite. A female sponge moth can lay one mass of eggs that can produce 1,000 offspring. We have a scientist to thank for the infestation, as the gypsy moth was introduced to North America by "Professor L. Trouvelot in a misguided attempt to breed a hardy silkworm." Some got out and destroyed vegetation in the area of his home in Massachusetts. You can read about him here. 

The caterpillars were so prevalent, they got on our utility and linen tubs, the car, camper, water jug, and pretty much everything. They left excrement on the car, and probably the camper. Washing the car the day after we got home, I found their excrement hard to clean off. A hose would not simply wash it off. I double and triple checked everything before heading home to assure we were not bringing home any stragglers, but I did find one after setting up the screen tent to let it dry. Scoundrels, they are.

I wrote this before going camping in northeast WI, and low and behold what did we discover for the first time at this campground, the very hungry Gypsy moth. As careful was we were to clean all our gear of the caterpillars, it is possible some dropped on the camper or car as we pulled out or even loaded. When I first saw one at the NE WI campground I wondered if it was a stow-away. They became too numerous, and while not as prevalent, or as large as those at Mirror Lake, they were still destroying tree canopies as I could tell by the leaf detritus on the ground and camper. Here again, we cleaned our gear before loading up. Yes, they are scoundrels, and it shows the damage and expense of introducing new species to the continent on which they were never before located. 

* When looking up a bit of information on Eric Carle's children's book, I was surprised to read that it had been affected by cancel culture's thought police, as it was banned in some libraries for not being sufficiently "inclusive and equitable. "  It is in good company, as other banned books included notable works such as the Harry Potter series and the Diary of Anne Frank.