I was out supervising the neighbourhood kids bicycling in the back alley when I noticed a very interesting caterpillar on the leaf of a lamb’s ear (Stachys byzantina) in our rather wild roadside flower bed. Several of the kids took a break and had a closer look at this striking caterpillar and one mentioned that he had seen several similar looking ones in his yard across the street.
A quick reference to the Insects of the Pacific Northwest and I was able to tentatively identify it as a forest tent caterpillar (Malacosoma disstria). According to Peter Haggard, this caterpillar is “the most common tent caterpillar on the coast.”
Field marks include the row of white “keyhole” like spots on the back of the caterpillar and the broad blue strip bordered by yellow-orange stripes on the sides. The food plants of this moth larva are alder, willow, oaks, and California lilac. We’ve got both oaks and California lilac on our block so it’s possible this little fellow was traveling too or fro.
Unlike other tent caterpillars, apparently this species doesn’t make a large, easy to see tent-like structure on the plants it is feeding on. I’ll have to look a little more carefully and see if I can find some others in the neighbourhood. And in mid-July and August, I’ll have to keep an eye out for the adult moths.