Bugging You From San Juan Island

I found this specimen at the Friday Harbor Post Office yesterday and picked it up to save in my collection. It’s a bit bird-pecked, but worth keeping for passing around at my upcoming insect talk at the library in October.

Lots of folks emailed me earlier in the year with photos of caterpillars they were finding. The larval form of this moth looks like the two photos below, depending on the developmental instar.

These moths are fairly common throughout the San Juan Islands. The larvae feed on Douglas Fir (Pseudotsuga menziesi) and other conifers. The name, argentum comes from Latin referring to the silver spots on the wings of adults.

While larvae are defoliators, they are not usually present in high enough numbers to cause economic damage or require any chemical control. Also, while very pretty to look at, the caterpillars do have urticating hairs which can cause stinging, burning, or rash in sensitive people. Take a photo or observe them, but resist the temptation to pick them up!