Louis N. Sorkin, an entomologist who volunteers with the American Museum of Natural History, started getting emails about the bugs swarming New York City yesterday but couldn’t identify them based on photos alone. So I sent him a close-up from the amateur documentarians on sub-Reddit NYCbike, members of which were getting caught in clouds of flies. “These are aphids,” Sorkin said, confidently. “I’ve never seen such large numbers before.”
Plant-lovers, rest assured. “The kinds of aphids that are a problem in gardens — I’ve never seen this kind of population explosion, and it doesn’t feel like the right time of year for those ones either,” says Sam Anderson, an expert in urban farming with Cornell Cooperative Extension. “I would expect some sort of predator to capitalize on this.” Which is why he thinks a summer boom in ladybugs is “not out of the question.”
To find out more about why the aphids may have suddenly appeared, Sorkin suggested I call Integrated Pest Management at Rutgers University, whose researchers look at bugs that affect our ability to grow plants and food — including aphids. There, I found George C. Hamilton, a professor in the Department of Entomology, who got his master’s degree by studying a species of aphids that feeds on sorghum and his Ph.D. focusing on a species that feeds on apples. Here’s what he had to say about the sudden aphid explosion.
What are these things?
Aphids. Which are totally different from flies, because aphids have sucking mouthparts. They feed on a variety of different plants and remove fluid from them. They are actually related to the spotted lanternfly, if you’re familiar with that insect.
Of course! I live in New York City! So why are we seeing so many of them right now?
In the spring, when temperatures are normal — in the 50s and 60s — it may take newly born aphids a couple of weeks to reach the adult stage, but as it warms up, that period may shrink to maybe a week instead of two weeks. These aphids do not reproduce by mating. One female can produce, say, 30 offspring. Then every one of those offspring, if they become adults, can itself produce 30 offspring. You can see how quickly those populations get to a large size.
So because it has been warmer and wetter, the population just exploded?
The warmer it is, the faster they develop. I think that’s what we’re seeing.
And those unusually big populations are now just swarming?
Well, another thing is that aphids don’t normally have wings. Most of the time, they’re wingless. They only have a generation with wings when the population size gets very large. So they exploded in population, had a generation of winged individuals, and those winged individuals are now swarming. The good news is they don’t bite. They’re a nuisance, but they don’t bite.
As the planet warms, are we gonna see more aphid swarms like this?
I would say that, like with any other insect, we probably are going to see some changes in their behavior. We’ll probably see insects that are more common in the southern part of the U.S. start to move into our area up here.
Will the aphid swarms ever stop?
As long as the weather is conducive for them to survive, they will continue. They are active in some parts of the South year-round. So in the fall, when it starts to cool down, it will slow down, and they’ll reproduce normally.
But if it stays warm, will they kill all of New York’s plants?
No, no. Lots of insects feed on aphids. Ladybugs, for example. So there are things out there that should keep them under control.
This interview has been edited and condensed.
Updated July 11: The article originally misspelled the last name of the volunteer entomologist with the American Museum of Natural History. He is Louis M. Sorkin, not Louis M. Sorokin.