Carrot-Seed Moth
Back to the porch light on August 10, 2014, we drew in this white moth overnight. Looking at it, my first thought was, “Oh no, not another one of these plain white ones. I’ll never ID this!”
But then, I used Google to do a site: search of Bugguide.net for “white moth michigan”, and . . . there it was, fourth image. Exact match, right down to the wing vein pattern and the way it drapes its antennae down its back. It’s a Carrot-Seed Moth, Sitochroa palealis
And, while reading up on it, I saw a picture of the caterpillar, and I said to myself, “waaaaaiiiiit just a minute here, haven’t I seen those before?”
The answer is yes. I posted pictures of the caterpillars just a few months ago, back in October. They look like this:
So, now we have a set! These moths are invasives from Europe, but are not really a problem because their host plant (mostly “Queen Anne’s Lace”, or “Wild Carrot”) is also an invasive from Europe. And I wouldn’t consider them a garden pest, because they only feed on carrot seeds, which is not the part of the carrot that we want to eat ourselves (and in fact, carrots are best eaten before they even flower, so garden carrots are of little to no interest to these moths).
Boy, they look to be spreading fast, though. It says on their page at the Moth Photographers Group that they weren’t reported in North America until 2002, and here they are in the UP already just 12 years later! This looks like a classic invasive species population boom, pumped up by the fact that their host plant is so very well established, and has so few other things that feed on it. It’s the invasive species equivalent of spreading gasoline all over an area, and then dropping a lit match on it. So we’ll probably be seeing them by the millions soon. I expect that probably within a year or two, practically every Queen Anne’s Lace seedhead will be full of their caterpillars in the fall. This will continue until they either knock back their host plant, get preyed on by something else, or they get an epidemic of some disease and their numbers drop back to something sane.
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In Florida we have several native plants in the carrot family which support the black swallowtail. Hope these seed eating caterpillars don’t cause a problem for them.