Return of the Tent Caterpillar

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.

Forest Tent Caterpillar (Malacosoma disstria)
A distinctive coloured tent caterpillar, the Forest Tent Caterpillar (Malacosoma disstria) has a series of white spots down its back and a striking blue stripe on its side.

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.

1 comment

  1. Found Several of these in the Ft Worth, TX Botanic Garden April 11, 2015 & took several pictures, but the light was fading and the area was shaded in the aroma garden behind the restaurant. Although Dave’s good photo shows that the blue stripes to be distinctive, we didn’t notice them immediately. Great pic! Now I can ID mine. Thanks.

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