A species of ladybeetle called the Asian ladybeetle (Harmonia axyridis), distinguished by the black "M" marking on its head, is leaving its mark this summer by biting people.
Entomologist Alejandro Costamagna says the species was first brought over in 1916, but the first established population appeared in 1988 to control pests on orchid fields down south. He notes the Asian ladybeetle has since migrated and are good for controlling aphids in crops such as soybeans.
"Their population explosion is typically associated with the invasion of soybean aphids. So, when this pest (the aphid) in 2000 was first detected in the US, the midwest, and expanded very rapidly to Ontario, Quebec, and Manitoba, then that's when we saw a change in the populations of Harmonia."
Costamagna says there has been an outbreak of aphids in soybean fields this summer and the number of aphids present directly correlates to the number of Asian ladybeetles.
"What happens is this soybean aphid, which we think doesn't overwinter here, this year, with the low temperatures in the past winter, they might have overwintered better. So, we don't know exactly why, but we know we have a large population of aphids. When that happens is when these ladybeetles come into play, they feed on the aphids and multiply their populations to very large numbers."
As for biting, Costamagna notes it's an unusual behaviour adding he has been working with ladybeetles for over ten years and has never been bitten.
"The only thing I can think of is on very, very hot days like we had on Tuesday, and when it's dry, that's when they become more restless. They are just trying to find a source of water and they may try different things."
He says they're completely harmless.
Poulin Pest Control director of operations Taz Stuart says in the fall the Asian ladybeetles will start to overwinter and may find their way into a garage, shed, or home.
"There are a couple things [you can do when they're in your home]. You can get a contact insecticide to treat them with or the old fashion way, you can get a vacuum and suck them up. You don't really want them inside in winter, if they do have to die over winter, they will start to smell. [To avoid them entering your home] make sure your windows, doors, any cracks or crevices are sealed up."
Costamagna says it's best not to squish them as they release a pungent odour similar to a stink bug.
"They're very visible and bright and beautiful and there's a reason behind that. They're advertising their presence to birds and that's because they have toxins. So, if the birds eat them they will become very quickly distasteful for the bird. The bird will learn the pattern of colouration and avoid them in the future."
He notes in very rare cases people can have an allergic reaction to the Asian ladybeetle bite or to the liquid they emit when feeling threatened.