It can be hard to believe that a cute little caterpillar can actually be very destructive.

A caterpillar you may have seen in the Biosphere is the spongy moth caterpillar. The spongy moth is a destructive, invasive species in Ontario. It starts its life as a very small, dark, and hairy caterpillar. When they get bigger, you can see five pairs of blue dots followed by six pairs of red dots on its back.

If you see one of these caterpillars, be careful not to touch them. They have small hairs which, when touched, can create a stinging feeling on your skin. These hairs can also leave you with itchy or uncomfortable rashes.

A spongy moth caterpillar crawling on a small branch. Photo by zoosnow 

Each of these fuzzy caterpillars has the ability to eat one square meter of tree leaves before adulthood. If only one can eat that much, imagine how many tree leaves a group of 100 spongy caterpillars can eat. Their favourite trees to snack on are sugar maples, oaks, elms, birch, pine, and spruce. Most of these trees can only survive maximum three years in a row with no leaves. A pine or spruce tree may not even survive one year.

In July, these caterpillars turn into cream or brown moths, and will only live for a few weeks. These moths can’t eat leaves, but will  reproduce and lay 100-1000 eggs!

The spongy moth is an invasive species which means it didn’t originally come from the area, and is also causing harm to the local environment. The spongy moth was brought to North America in the 1860s, but it wasn’t found in Ontario until 100 years later.

Luckily, spongy moths have a number of predators including a virus, a fungus, a small wasp, and a few mammal and bird predators. These predators mean there are less caterpillars to eat the leaves.

Spongy moth caterpillars eating leaves. Photo by Katrina Krievins

Activity Time! 

How can you protect and save your favourite tree?

  1. Find a bucket that will be able to hold the egg sacs
  2. Look closely at each tree on your property or nearby and you will see light brown fuzzy-looking sacs on the tree
  3. Use a butter knife or a popsicle stick to scrape the eggs off the tree into the bucket *Do not do it on a windy day as sacs will blow away and spread*
  4. Mix the eggs with soapy water and leave it for few days
  5. Dispose of the contents down a drain

Bonus! Learn more in GBB’s Spongy Moth Information Package

Spongy moth egg sacs on the bark of a tree. Photo by Joshua Giesbrecht