The Backyard Arthropod Project

S_ was growing some petunias in pots on the south side of the house last spring, and one day noticed that she had quite an infestation of some pretty eye-catching caterpillars. You can see three of them just in this one picture[1], there were probably a dozen or so in total:

In addition to being brightly colored, they were covered with black, spiky protruberances:

When touched, they immediately curled up in a ball, with the spikes sticking out, and stayed that way a long time

A distinctive caterpillar like this is a snap to identify, because people take pictures of them all the time. It is a Variegated Fritillary, Euptoieta claudia, and Bug Guide has pages and pages of pictures of the caterpillars, pupae, and adults. Of course, I didn’t know what they were at the time, now I’m sorry we didn’t try to rear some of them to get pictures of the whole life cycle.

I’m a little surprised that I can’t find any reference to fritillary caterpillars eating petunias, either on BugGuide or in “Caterpillars of Eastern North America”. They’re supposed to be more partial to violets and pansies. In fact, about the only reference to a similar caterpillar that does eat petunias is way down near the bottom of this list of butterfly foodplants - they say that the common buckeye caterpillar eats petunias. The thing is, the common buckeye caterpillar looks generally similar to the fritillary caterpillar, but the colors are wrong and it doesn’t have the particularly elongated spikes over the head that the fritillary does.

At any rate, I know that I’ve seen the variegated fritillary adults flying around, they are very common, and if it wasn’t for the whole food plant issue I’d have no doubt at all about what these caterpillars were. They evidently breed fast enough that they have about three generations per year, and so we see the adults pretty much all summer long.

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[1] I tried photographing these on their food plant, without the macro lens, because its limited focus travel and bulkiness make the lens awkward to use. While the pictures came out good enough to identify the caterpillars, I’m a bit disappointed with the level of detail. I need to either practice using the macro lens in the field, or be sure to bring things indoors to use the macro rig, even if they are fairly good-size insects.

Other articles related to this topic:

• St. Lawrence Tiger Moth Caterpillar (?)
• Black-Etched Prominent Caterpillar
• Linden Looper Caterpillar (Inchworm)
• Ctenucha virginica caterpillar
• Caterpillar hunter beetle