Disgusting undulating masses of red and black insects are swarming around Toronto, part of an invasive expansion of the critters known as firebugs (Pyrrhocoris apterus).

European firebugs are native to the Eurasian continent, and have found their way across North America in recent years — an invasive push that includes Toronto.

Considered relatively harmless to the local ecosystem, firebugs feed primarily on seeds and mallows, and can be found in Toronto feasting on species including linden trees and tree of heaven.

Officials aren't particularly worried about the spread of firebugs in the Greater Toronto Area. The City of Vaughan even states that firebugs "are harmless and do not need to be reported" to City officials like other species of invasive insects found in the region.

Though their diet and behaviour are unlikely to cause harm to the established ecology, the way the insects congregate in wriggling masses is sure to unsettle some.

Firebugs emit a chemical messenger pheromone that calls the insects together to form large gatherings. Other chemical signals produced by firebugs include alert pheromones that send these large aggregations scattering in all directions in the presence of a predator or other threat.

One of their most fascinating evolutions is a state similar to hibernation called "diapause" that allows the insects to survive cold winters — perfectly suited for their rapid spread through regions like the GTA.

Sightings have grown increasingly common since 2018, and the firebug population seems to only be growing as the distinctive red and black critters further establish themselves among the native fauna.

Who dis? East Toronto
by u/lvoryPanda in whatisthisbug

You don't have to comb through the brush to find them either, as firebugs have even been spotted amid the hustle and bustle of downtown Toronto.

Fire bug (?) found in Toronto along Jarvis. was among about 20 others all spaced out. Never seen one live, thought it was worth a post to shoutout this invasive species.
by u/RexdaleRebel in toronto

With little threat posed, it's a tough call whether to include this invasive insect on the must-squish list, earning it a rare 'squish at your own discretion' judgement.