Waved Sphinx
Sam caught this big sphinx moth when it came to our porch light on June 28, 2014. Comparing it to the palm of her hand, it looks to have a body nearly two inches long.
The coloration was pretty muted, with a couple of thin yellow “eybrows” visible in front of the incipient bald patch on the thorax.
There are no mouthparts visible, so it is likely that this is one of the sphinx moths that doesn’t feed as an adult.
The antennae are thin, with a white stripe running along them.
And, the abdomen is gray with no colored spots, which narrows down the potential ID candidates considerably.
I think this is most likely a Waved Sphinx, Ceratomia undulosa, one of the most common large sphinx moths in this area. The coloration on the wings is pretty variable, and in fact the one we caught back in 2009 looked quite a bit different (although it still had the white-striped antennae, the yellow “eyebrows”, and the dark patch on the thorax).
As I mentioned on the previous outing with this moth species, it is reported to eat, among other things, lilac. Since nothing much else eats lilac, and we have it all over the place around here, I should try beating one of our lilac bushes next summer to see if we can get any of these caterpillars out of it.
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I’d recommend against beating the lilac bushes. One of our neighbors did it and he was hauled up before a judge in the Hague on charges of torture. However, if you’ve got a hose, you can waterboard them and make it look like you’re cleaning off the leaves.
Hey, like Groucho said once, they can’t all be good.
Seriously, is the bald spot a marker of a sphinx moth? I’m sorry if you’ve said that before and I missed it. I typically read your excellent blog while I’m having my first morning coffee so the old synapses are just warming up.
As far as I’ve been able to find out, the bald spot is a common occurrence in many kinds of moths, and looks to be a sign of age. For some reason, the hairs on the back of the thorax just seem to be more prone to come off than hairs elsewhere on the body. It might have to do with them being more exposed to damage (possibly due to standing up straighter on that particular smooth exoskeleton plate); or maybe there is a lot of air turbulence pulling the hairs back and forth during flying due to being right next to the wings, and they snap off; or maybe they just fall out once a moth gets flying to allow the flight muscles to cool off better; or they could even be lost in tussles with predators, or with other moths (either during mating, or while fighting with each other over mates). Until somebody actually buckles down to seriously study the effect, it is hard to say.
The one thing it doesn’t appear to be, though, is a useful ID feature (unfortunately).
Maybe it’s just a design flaw. A friend of mine used to say, “Biology is a kludge.” I feel like we always need to find some kind of explanation for these things when in fact, evolution is a clumsy, messy process.
All we know for sure is that single-celled algae was one heck of a design. Look how long it’s managed to stick around!