This summer, many millions of gypsy moth caterpillars have emerged across Ontario, causing ecological concern from North Bay and Sault Ste. Marie to Windsor and Ottawa.
Gypsy moths (Lymantria dispar) were introduced to eastern North America from Europe in the late 1800s through a failed attempt to harvest silk from gypsy moth cocoons.
These invasive caterpillars damage native trees and shrubs, destroying habitat and food sources for wildlife by consuming foliage including oaks – the preferred host plant for gypsy moths. Rural and urban areas are teeming with the caterpillars, which disturb residents with vast quantities of caterpillar feces and by covering external walls with dense infestations as larvae look for sites to turn into moths.
Supporting habitat and healthy habitat for local wild species that predate gypsy moths could be helpful both for the wild species themselves and biodiversity more broadly by controlling gypsy moth populations.
Chickadees will eat all life stages of the gypsy moth. Blue jays, eastern towhees, red-eyed vireos, grey catbirds, Baltimore orioles and black-billed and yellow-billed cuckoos will eat gypsy moth larva and adults. Indigo buntings consume hairy caterpillars including those of gypsy moths. Robins are an effective predators of gypsy moth larva, pupae and adults too. White-footed mice also eat gypsy moth larva, pupae and adults. American and Fowler’s toads regularly consume gypsy moth larva and adults. Interestingly, carpenter ants will also eat gypsy moth pupae and eggs.
Gypsy moths overwinter in the egg stage on tree bark or buildings. Eggs hatch and larvae seek foliage to consume in spring. Gypsy moth larvae mature in July and often grow to be five centimetres long, at which point they metamorphize into pupae. Moths emerge and mate mid-summer and then lay egg masses on trees and sheltered areas. Gypsy moth outbreaks tend to occur every five to seven years.