Gorgone Checkerspots Break Diapause

Gorgone Checkerspot (Chlosyne gorgone)
Image from wisconsinbutterflies.org

Gorgone Checkerspots are rare in northern Illinois. Years ago, my very first experience with butterfly translocation was to help Ron Panzer try to establish a population at Nachusa Grasslands. Last summer, we began a project to attempt breeding this species in the lab. We obtained a gravid female from a railroad prairie in Grundy County, and got dozens of eggs from her. About half of the larvae went on to complete their life cycle. The other half went into diapause (a general cessation of activity) sometime in August.

Larva Land - Wintering Cages at the Portland Zoo

In September, Vincent and I visited the Portland Zoo to learn techniques for holding larvae over the winter. It's a process we continue to struggle with. They were using a technique where caterpillars are placed in yogurt cups and stored outdoors under inverted terracotta flower pots for the winter. They were having success with a close relative of the Gorgone Checkerspot, so we decided to give their technique a try.

All winter long, our Gorgone larvae have been under flower pots on the museum roof. Last week, we realized that their host plants had sprouted sufficiently for us to try waking them up. We put them in caterpillar rearing cages with purple coneflower leaves. For several days, not much happened. On Thursday, I suggested that Vincent move a couple of the cages into direct sunlight. Several of the caterpillars promptly molted. On Friday, everyone went into the sun.

Gorgone Checkerspot larvae on Purple Coneflower leaves (5/9/09)

Today, all of the surviving larvae have molted and begun feeding. You can see all the frass (insect poo) and a shed skin on the bottom of the cup in the photo above. I had no idea that molting would be the first step that would happen when the larvae broke diapause. A brief shot of direct sunlight seems to be essential in the process. About half of the larvae that we placed outside survived the winter (that's reasonably good, especially for a first try). We will repeat the experiment on a larger scale this year. There are several hill prairies in northeastern Illinois that could soon be home to new populations of this lovely species.