T. theona life history
Theona Checkerspot (Thessalia theona) Life History

10-20-09, ovipositing


10-23-09, about to eclose

10-24-09, the caterpillars have just emerged





11-8-09, turns brown when about to shed skin


11-12-09, mature caterpillar

11-13-09, chrysalis

11-21-09, butterfly ready to eclose


11-21-09, fresh Theona Checkerspot

One evening in October, 2009, I was fortunate to observe the female in the first picture fly to a small Purple Sage, Leucophyllum frutescens. She disappeared into the plant, but I soon found her crawling around near the base. I wasn't sure whether she was ovipositing, so I took a few pictures to record both the female and the location. The next day I returned and found the eggs.

The caterpillars emerged after only four days. They went through a series of color transformations as they matured: green-yellow to white to black-spotted silver to the mature silver-spotted black. The heads did not turn turned red until the last or second-to-last instar.

I returned most of the caterpillars to host plants after a few days.

The first caterpillar to pupate did so 20 days after it emerged from the egg; it emerged for the chrysalis six days later. The rest of the caterpillars followed a day or two later. The journey from egg to adult took 30 to 32 days.

Theona Checkerspot Page