Fuelled by hot, dry summers and tempting oak woodlands, gypsy moths and their munch-happy larvae have reached infestation levels in Mississauga’s forests. City workers have even taken the rare step of aerially spraying infested areas. And it’s not only the beleaguered burb’s trees that are threatened, it’s aesthetic sensibilities—the moths are also seriously disgusting. Up close and personal with the bug that (almost) ate Mississauga.

Egg Masses
Female gypsy moths deposit egg masses in mid-summer on tree trunks, fences and even cars. (Drivers are often unwitting importers of gypsy moths.) They gestate over the winter, protected by scales and hair shed from their mother’s abdomen. Spongy and tan-coloured, the egg masses range from nickel- to toonie-size and can contain anywhere from 200 to 1,000 eggs; the City of Mississauga has discovered single trees with as many as 800 masses—meaning some could host up to 400,000 hungry larvae.

Larva
Gypsy moths go through four stages of development: egg, larva, pupa and moth. It’s during the larval (or caterpillar) stage that they wreak havoc. Though they favour the leaves of oaks, elms and maples, they’ll dine on more than 300 species of tree and shrub. A single larva is only about the size of a pinky finger, but when it gangs up with its brethren, it can significantly affect a tree’s ability to nourish itself, leaving it vulnerable to attack from other pests and bacteria and potentially killing it outright.

Dung
Gypsy moth larvae don’t just make a mess of trees. Tiny curls of their fecal matter rain down from infested flora, leaving a trail of half-digested leaves in pools and on lawns and patio furniture. Adding insult to repugnance, the husks of shed skin and hair they leave behind—gypsy moth larvae molt or outgrow themselves up to six times during the seven-week larval stage—can cause allergic reactions in humans (especially kids), ranging from rashes and welts to shortness of breath.

Moth
Larvae eat non-stop, but after two weeks in a brown cocoon, the full-grown gypsy moth lives only to breed. To attract gentlemen callers, female moths release a potent sex pheromone. Male moths answer the siren song via elaborate feathery antennae that allow them to detect the scent of game females from long distances. The act begins only after the female lifts her wing, giving her partner the thumbs-up. Mating can take up to an hour—a substantial time commitment given that the gypsy moth lives only seven days.