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As temperatures drop and students brace for the return of triple-layered sweaters and snow boots, one aspect of summer lingers on campus. Despite the change in season, ladybird beetles are still abundant at McMaster. A quick Twitter search of “ladybug” reveals the annoyance and frustration of many as the beetles have suddenly reappeared in windowsills and corners across southern Ontario.
Marvin Gunderman is annoyed for another reason. McMaster’s in-house entomologist has been captivated by beetles, bugs and other invertebrates since he was a child and corrects the layman’s name “ladybug,” preferring the more correct “ladybird beetle.” “They are true beetles. They have wing-covers that meet in a straight line down the back,” he explained.
Ladybirds are summer insects, seeing out their entire lives from nymph to adult. “They're a bit unusual, because in the insect world, the nymphs and the larvae are the eating stage. The adults basically just mate and disperse,” Gunderman said. Ladybirds rely on their fat stores to help them survive the cold Canadian winter, and to ensure those fat stores are full, both the larvae and adult ladybirds are powerful hunters, an oddity in the insect world. They both feed on aphids and soft-bodied insects.
Interestingly, the species of ladybird invading lecture halls right now is not domestic. The Asian ladybird beetle has been established in Canada for around 20 years according to Gunderman. The species was originally brought to the western hemisphere to protect tobacco and soybean plants from aphids that feed on crops. However their population grew too difficult to control. “They're prolific breeders. They're very aggressive and they've pushed our native species to the sidelines. They're still around, but in lower numbers,” Gunderman said. Asian ladybirds are typically bigger, with larger mandibles that can actually bite a person, unlike their more local relatives.
Gunderman also had an explanation for their appearance. “The swarms that you're seeing late right now is just a pre-hibernation thing,” he said. That said, due to the cooler temperatures prior to last week, the ladybirds were likely already in hibernation. Gunderman explained that when conditions are favourable, the beetles will come out of hibernation to enjoy the warm weather.
However, this premature revival is detrimental to the ladybirds. Gunderman said, “They need to stay chilled over winter because they only have so many fat reserves. If they're active too often, that means they use the body fat and they have less to ride out the winter. If they don't have it, they'll just die.” This explains the inevitable doom of ladybirds who manage to stay inside a house in the winter. Unless the house's plants have aphids, the ladybird will use its fat stores and die of starvation. Gunderman advised the kindest way to treat ladybirds found in the house is to bring them outside.
While it is unusual for ladybirds to be so prevalent so late in the year, their presence is not a sign of the apocalypse. “It's a very common occurrence, this swarming behaviour. Even prior to the Asian ladybird, we'd still have our native species do the same thing. But with more of the Asian ladybirds, we're just seeing it in more noticeable numbers.”
Gunderman predicts that if Ontario experiences a warmer winter, fewer ladybirds will hibernate properly, leading to a reduction in next year's numbers. “Right now we just have a beautiful warm spell in the weather, so insects are going to be active.”
Photo Credit: Jon White/Photo Editor