Wild Profile: Meet the cecropia moth

A cecropia moth sitting on a maple leaf By Cathy Keifer/Shutterstock

As May heats up, the huge, dramatic-looking cecropia moth—Canada’s largest moth—appears on the scene. It emerges from its massive cocoon in late spring or early summer. Cecropias stick around only long enough to find a mate and breed, leaving behind hundreds of leaf-munching offspring.

How big is the cecropia moth?

This moth is part of the giant silk moth family; they get their name from the huge, elaborate cocoons that they spin. Big cocoons produce big moths: cecropias have a wingspan up to 18 cm—that’s about the size of a plate. (A monarch butterfly’s wingspan, for comparison, is only 9 or 10 cm.) The moths are nocturnal, and have only vestigial mouths. They don’t eat. Their main job is to find a mate and get down to, ahem, business. Males do the pursuing. Newly-emerged cecropia moth females produce a pheromone from their abdomens. Males, using their feathered antennae, can detect one drop of the natural chemical from a kilometre away.

Cecropia moth females vs males 

Female cecropias weigh almost twice as much as males. That’s because they’re laden with up to 300 unfertilized eggs. That’s a lot of babies! Once they’ve made a love connection, male and female moths hook up for almost a full 24 hours. Then, males leave to find more potential partners. The female lays her now-fertilized eggs in batches, often on maple, birch, or cherry trees. Jobs complete, life is short for these bugs. Both parents die within a week or two.

What do the caterpillars look like? 

A female cecropia moth lays more than a hundred eggs, but many caterpillars don’t survive long enough to become adults. When they hatch, they’re tiny and black. They go through several successive molts, changing from yellow to green. Eventually, when a caterpillar is about five inches long, and fattened up from two straight months of eating, it begins to spin its cocoon. It takes a full day, and nearly a mile of silk. Home complete, a cecropia moth caterpillar seals itself into the cocoon for the winter. Nighty, night! See you next year.

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