Wednesday, May 25, 2016

Toxic Mimic

Turning over leaves while looking for butterfly eggs I was startled to see the Orange Patched Smoky Moth - Pyromorpha dimidiata clinging in the shade.  It hung on patiently as I removed the leaf to get better light and remained there when I put the leaf back on the branch.

Lycomorpha pholus - Cyndy Sims Parr
P. dimidata is a common day-flying moth which ranges from Missouri to New York.  Its peak time is May to June and it tends to be on oaks.  Adults eat nectar while the larvae feed on leaf litter, especially oak.

To my eye it is almost a twin to the Black-and-yellow Lichen Moth (Lycomorpha pholus) and I can't find a side-by-side comparison.  I based my ID on having found these repeatedly in our oak/hickory forest while L. pholus is a prairie species that flies in late summer.

Calopteron terminale - Wikimedia

Its bright coloration is aposematic, warning off predators of a potential toxicity.  It looks similar to the Lycid beetles of genus Calopteron and some sources call this Batesian mimicry, a harmless species getting protection by mimicking a toxic species.  Lycid beetles contain pyrazines, an odoriferous chemical which serves to protect them from predators.  In this case however, this is Muellerian mimicry as our smoky friend is toxic on its own by manufacturing hydrogen cyanide!

A final note, the look-alike moth Lycomorpha pholus does not produce toxins so you might feel free to sample it this fall, if you are so inclined and are certain of the identification.

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