Caterpillars

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.

Flitting, dodging, never seeming to land, northern spring azures are ethereal specks of splendour, appearing miraculously on sunny, warm spring days. The pale blue butterflies herald the unfolding of the season’s ephemeral blossoms—to which they’re intrinsically tied—along forest trails and watersides throughout Canada to the tree line.

Beneath sun-warmed leaf litter, azures emerge from plump, brown or yellowish chrysalids for their maiden flights, unlike the smattering of other early spring butterflies, which overwinter as adults. Males patrol almost constantly for mates, especially mid-afternoon to dusk. They seem to disappear when occasionally landing to bask, the grey-brown undersides of their closed wings blending with ground colours. Living for only a few days to a couple of weeks, they sip a little flower nectar, but tank up on minerals from mud puddles or even animal droppings.

Female azures, distinguished by their black-bordered forewings, generally mate within hours of emerging. The following day, they lay light-green eggs, spaced individually on flower buds of wild cherry, blueberry, dogwoods, and other shrubs with white spring blossoms. They perish soon afterwards.

Their tiny, squat caterpillars, which can be green to whitish, pink, or brown, hatch within several days, and munch buds, flowers, and developing fruits for two to three weeks before they pupate. As they grow, they secrete a greenish honeydew solution, favoured by sweet-toothed ants. In exchange for the sugary drink, the ants protect the developing pupas from spiders, wasps, and other assailants.

While most northern spring azures stay cooped up in chrysalids for 10 or 11 months of the year, some in southeastern Canada pupate within only a few weeks and fly in summer. In southern Ontario and the prairies, a nearly identical but apparently separate species, the summer azure, also takes wing around the same time.