If you spotted this insect on a blackberry leaf, as I did last week at Mount Pisgah, you would probably keep moving, and maybe even quicken your pace, to get out of the way of the yellow jacket wasp. And this particular moth would be satisfied that you did.
That’s right. This is a moth. A clearwing moth in the Sesiidae family, to be exact, and all of them are excellent wasp and bee look-alikes. Some of the bee mimics even have ostentatiously fluffy hair on their back legs, to imitate pollen-carrying bees.
These moths have common names corresponding with the food their larvae eat. There are Douglas-fir, currant and fireweed clearwings in Oregon. The first two photos are a Raspberry Crown Borer moth, or Pennisetia marginatum. When it’s a caterpillar, it enjoys eating cane fruit roots, including blackberries. In fact, this species was introduced to Hawaii to help keep the non-native blackberries from taking over. I’m guessing it didn’t go so well, since our Himalayan blackberries seem to be thriving. The adults live very short lives, just long enough to mate and lay eggs.
Looking at the moths from the top, you can see why they’re called clearwings. It turns out, butterfly and moth wings can function just fine without their scales, and there are species of both that do without them. Many butterflies and moths lose scales as they get older as well.
According to records posted on BugGuide and iNaturalist (two helpful and accessible citizen science sites), Raspberry Borers are visible through September in Oregon. Other species, like the Strawberry Crown Borer, Synanthedon bibionipennis, show up earlier in the summer (second two photos). I found the mating pair of Strawberry Crown Borers near the lily pond at Mt. Pisgah in July. The female is the larger one, on the right. Strawberry Borers are smaller than Raspberry Borers, and they have a fan of feathery hairs at their “tail.” Their larvae eat plants in the rose family, as well as the tops of strawberry roots.
Stay curious!
Sources:
The Bug Lady’s explainer on Raspberry Crown Borers. https://uwm.edu/field-station/raspberry-crown-borer/. Accessed 9/3/21.
Glorious Squash Vine Borer (a gaudy bee mimic): https://bugguide.net/node/view/484436/bgimage. Accessed 9/3/21.
