I remember what it was like: all of the sudden, the trees were furry and leafless. The houses, normally light in color, turned dark with writhing insects. And the sidewalks and streets were smeared in dead caterpillar juice and their droppings. This was my first (and only) caterpillar invasion, and it left quite an impression. My 10-year-old mind was blown — and utterly fascinated.
It was the end of the ‘90s, and I was visiting my relatives in Rouyn-Noranda, a city in northern Quebec. As a child, I loved bugs and what most people would describe as "gross stuff," so insects generally didn’t faze me. But in this case, it was hard not to get nervous walking around a neighborhood block: every step could leave your shoe covered in caterpillar gunk, and tree branches would get so heavy with these critters that "chunks" of balled up caterpillars would fall off — straight onto people's heads.
If you’ve never experienced a caterpillar outbreak, this probably sounds really weird. But this is what the Canadian province of Saskatchewan is dealing with right now. People there are in the middle of one of the worst infestations the province has seen in a decade, and it's intense. Just look at this picture of the entrance to a women's bathroom at a local campground.
So, in honor of the outbreak, here’s a quick and dirty guide that explains what’s going.
Oh god, what’s with all the caterpillars?
The caterpillars in these pictures are "tent caterpillars." They reproduce once a year, but their numbers tend to increase over time, so every 10 to 15 years, they cause large outbreaks that can last about three to six years. Natural controls, like cold weather or disease, are usually responsible for ending the outbreaks.
In Saskatchewan, the outbreak is in its third year. But that doesn't mean the caterpillars are present year round. Their entire life cycle lasts about six weeks, so they don’t cover trees for too long. Once they’re done being caterpillars, they grow cocoons. Five to 10 days later, brown furry moths emerge to lay eggs; the moths live for less than week. Most of the caterpillars in Saskatchewan should be gone by mid-June.
Okay, but why is this outbreak so bad?
The weather is probably to blame. Saskatchewan experiences a mild winter and hot spring, the CBC reports — exactly the kind of weather that lets caterpillar eggs survive the winter in large numbers and hatch early.
Is this bad for the environment or people?
The current caterpillar "outbreak" in Saskatchewan is pretty bad. Some cities, like Regina, have been fighting back with pesticides, but others, like the city of Saskatoon, haven’t bothered. That’s because the insects don’t adversely impact the health of the trees they munch on; the caterpillar life cycle lasts about six weeks, so the leaves regrow afterward. And because the caterpillars tend to stick to deciduous trees, farmers don’t have to worry about their crops. The caterpillars are bad for horses, however; when mares eat them, they can cause the abortion of late-term foal fetuses.
This means that for most people, the caterpillars are just annoying — and those who aren't happy with having furry homes have to deal with them on their own. Ideally, this means that they will apply Bacillus thuringiensis kurstaki, a bacterium that kills caterpillars but that doesn’t kill other insects or damage surrounding vegetation. Unfortunately, it’s been hard to find in Saskatchewan recently; the pesticide takes six weeks to make, and it keeps selling out.
Fine, but it's still gross
My relatives are not impressed with these caterpillars either — so I feel ya. Here’s a GIF of yawning kittens. I hope it helps.