Wild Profile: Meet the clouded sulphur butterfly

The clouded sulphur butterfly doesn’t have a pretty name—but it is pretty. And it’s one of the few butterflies you’ll see in the fall. Like the mourning cloak butterfly, clouded sulphurs feed on late-blooming flowers such as purple aster; the last generation of caterpillars go into hibernation by the end of October, and stay that way until spring. The clouded sulphur’s name comes from their colour. At their brightest, they’re yellow like sulphur.

As in the bird world, the male clouded sulphur is flashier than the female, with brilliant yellow wings and a distinct black border. But the females are the ones who are dimorphic: they occur in two different colour “morphs”—pale yellow and nearly white. But look for the single black spots on each forewing; both sexes, no matter their colour, have these.

The clouded sulphur is widespread. Cottagers almost everywhere in Canada can spot them (they seem to only be missing from Labrador, the Arctic, and northern Quebec). Unlike other butterfly species—the monarch, for example—clouded sulphur numbers don’t vary much. The population doesn’t crash or boom as a result of an increase in predators, or a loss or abundance of food sources.

One possible reason for this equilibrium? They feed on a wide variety of nectar-producing flowers, along with milkweed, clovers, dandelions, thistles…the list goes on. And they’re well-adapted to living in different habitats: parks, meadows, stream banks, your garden…again, the list goes on.

The clouded sulphur is a fan of “mud-puddling”: getting nutrients from damp surfaces—puddles and mud—but also rotting plant matter, carrion, and dung. Gross, maybe, but it’s good for the butterflies and other insects that do this; they can obtain important salts and amino acids from the fluid that they suck up. We’d probably prefer the flower nectar, but hey, everyone needs a balanced diet!

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