Tent caterpillars appear early in the spring, They form tents of gray silk stretched out between branches of alder trees on the coast. This tent is used as a molting mat. Tent caterpillars are active all day, unlike most moth caterpillars.
In 2005, here in Campbell River, we had an incredible invasion of tent caterpillars. There were so many that you could not walk with out stepping on them, on the roads, there was a brown mush where the tires of vehicles road.
My plum tree was completely covered by silk and the nest of silk spread out for 5 meters into the yard in all directions from the tree, it was like something out of a horror movie. This was going on all over town. I thought they would never be gone but by two years later, they were almost completely gone.
The tent caterpillar moth has a wing span of 4 to 6 cm and is dark brown with 2 whitish lines nearly parallel to the outer edge of the wings.
It is wide spread in North America. The caterpillars can strip and kill a tree if too many feed on it.