A Complete Butterfly Life on a Single Day

Rarely do we see all these stages together at a single site. Sure, we see adult female butterflies laying eggs on their host plants. (Baltimore Checkerspots use Turtlehead [Chelone glabra] and a surprising diversity of other unrelated plants.) So finding adults and eggs together is nothing unusual. We might also see early-instar (tiny) caterpillars newly hatched from those eggs. But by the time those caterpillars feed and grow (for a month or so), and then pupate to form a chrysalis, many of the adults have died after their fling on the wing. So it’s often hard to see all the stages together.

Baltimore Checkerspot is a bit odd. Instead of overwintering—like many butterfly species—as egg or pupa, the Baltimore spends the winter as a caterpillar. By early autumn, the caterpillars I saw yesterday will stop feeding, drop to the earth near the base of their food plant, and overwinter in the leaf litter in a state of diapause. Next spring they’ll rouse to resume feeding, pupate, then emerge in late June or so to fly as adults, mate, and start the cycle again.

This odd cycle, I suspect, extends the period we see caterpillars among the other life stages. Or maybe this site in East Montpelier is simply so busy with Baltimores (swarms of them) that it’s easy to find all the life stages together. Whatever the case, enjoy the orange parade, starting with that mating pair above, and then below progressing from egg to larva to chrysalis to two final shots of an adult, which I photographed from above and below.