Tuesday, September 13, 2011

Unexpected Tiger Moth

This is a larva of the Unexpected Tiger Moth, Cycnia inopinatus, an Endangered Species in Ohio. Despite the name, its discovery at this time and place was not unexpected. I’ve been waiting for it to appear. I saw a mature larva earlier this summer, but couldn’t immediately identify it. By the time I discovered what it was, it was gone.

It was within this mass of Butterflyweed that I last saw one of these larvae. A little research revealed that the Unexpected Tiger Moth was double brooded in Ohio, so I was hoping that a new batch of larvae would appear. The larvae pupate in the leaf litter at the base of the food plant. I assumed that upon emergence, the moths would mate and lay eggs on the plants near their emergence site. Apparently that’s exactly what happened.

They’re a striking species with their bright orange bodies adorned with black spots that give rise to tufts of dark hairs. Toxins from the Butterflyweed make the larvae unpalatable, so the bright colors act as a warning to potential predators. Longer hairs project forward over the caterpillar’s head. These hairs may help conceal the movement of the head as the caterpillar eats. It’s fine to be nasty mouthful that predators won’t eat, but that doesn’t mean you can afford to be noticed by everything that wanders by.

Hair thickness varied between caterpillars. This probably has to do with the developmental stage of the individual. I counted at least two dozen caterpillars, but they were really hard to spot, so the count may be short. Their size was about half that of the one I saw earlier. I should be able to get a more accurate count when they get larger.

Now comes the question of how to manage this tiny area to the benefit of the moths. This clump of Butterflyweed is in the corner of my vegetable garden and the dried stalks would typically get mowed off and the litter raked away. This practice will have to stop now that I know there will be Unexpected Tiger Moth pupae hidden in that leaf litter. I should also see what can be done to increase the size of the Butterflyweed patch. It’s not often that the rarities show themselves in such a convenient location. I’m excited about the opportunity to observe and learn about such an uncommon animal.

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