How a warm winter can affect insects

Mosquito

By Jenna Wootton & Liann Bobechko

If you’re like us, the mild winter and the warm spell in March have had you thinking about opening up the cottage early this spring. And though the unseasonable weather may draw you to the lake sooner than normal, could it also mean a larger than normal horde will be there to meet you? We spoke with Doug Currie, curator of entomology at the Royal Ontario Museum, to find out.

Blackflies
Currie predicts that with warm temperatures in March, blackflies could be showing up in cottage country two weeks earlier than usual, settling in around mid-May. The cold snap that followed the warm spell won’t likely have killed off any significant number of blackflies, because they are still in their larval stage, and won’t have emerged yet.
But there’s good news too. With an advanced season, “they’re also going to be gone earlier.” While blackflies usually last until the end of June, an early onset would cause them to disappear before school’s out. Furthermore, they are very susceptible to drought and, Currie says, “Unless we see a huge amount of rain, I can say with confidence that there will be a huge die-off.”

Mosquitoes
Unfortunately, you still need to stock up on repellant. Though mosquito numbers are harder to predict than those of black flies, “mosquitoes will be with us until freeze up,” says Currie. “There’s no question about that.”
Even though he’s already heard of some early encounters with the bloodsuckers, because mosquitoes have multiple generations, it doesn’t mean they’re going to die off any sooner. The ones you’ll see waking up early are the overwintering adults. “If this first generation comes out too early, there might be mortality from a cold snap, but it won’t get all of them. Even if there are fewer eggs laid from the first generation due to some die-off, if the weather then turns wet, the population will probably go along tickety-boo.” The current dry climate may not be ideal for the later emerging populations, but they are not as susceptible as blackflies are. They will just wait until it gets wet enough, and, as Currie points out, conditions will inevitably change between now and late fall.

Horseflies and Deer Flies
Our mild winter may mean more overwintering larvae will have survived (we knew there would be a price to not having to shovel), but these guys generally show up later in the season, so the effects of an early spring aren’t likely to be as apparent. “That’s not to say there won’t be any impact,” says Currie, “but I don’t think it will be as marked as the insects that come out earlier.” This year, as always, you can expect those painful little bites left by these flies in July and August.

Of course, says Currie, all this speculation comes with a caution: “These predictions are all very weather and climate dependent.”