Why are cockroaches taking to the skies in New York?

Urban cockroaches are not good fliers, but the heatwave may be hot enough to prompt some to take evening flights to cool off.

A dreaded urban pest, usually relegated to sewers and garbage heaps, may soon take flight to the skies above.

In cool temperatures, American and German cockroaches prefer to travel by foot – unseen, save for a few unsavory household encounters. But on particularly sweltering days, these insects may emerge from their hiding places and take flight to cool off, a fact that has prompted New Yorkers to share their fears of a locust-like doomsday across social media.

But are those fears rooted in reality?

The American cockroach is just one of about 5,000 cockroach species, most of which live in the tropics. The vast majority fly regularly, and are actually quite good flyers. But over evolutionary time, many urban cockroach species have lost the ability to defy gravity.

“If you don’t use it, you lose it,” Coby Schal, a professor of entomology at North Carolina State University, tells The Christian Science Monitor in a phone interview. “If you don’t have a need for flight, there’s no need to invest a lot of resources in supporting those flight muscles. You might as well use those resources for something else, like reproduction.”

American cockroaches, for example, live primarily in sewer systems, where flying is unnecessary. These common insects are still capable of limited flight, but they generally prefer to stay grounded – it’s difficult for them to engage flight muscles in cold conditions. But as temperatures rise, they can activate these muscles more easily.

And in the wake of a recent Northeast heat wave, New Yorkers are especially wary of this fact. But notions of a “flying roach hellscape” are mostly exaggeration, Dr. Schal says, although more cockroaches will be out and about on humid evenings. 

Climate warming could change that, however. As temperatures rise at higher latitudes, even by just a few degrees, and the dog days of August persist with hot, humid nights, New York cockroaches may prefer to keep their legs airborne.

“I live in North Carolina, and the cockroaches here do not fly,” Schal says. “But in Charleston – not very far away – you can go out at night and see the American cockroach fly. That’s not a huge temperature change, going from North Carolina to Charleston.”

Cockroaches could be the latest in a long line of organisms that changed their lifestyles as a result of climate change. Earlier this month, it was discovered that the spiny damselfish could adjust its circadian rhythms to resist ocean acidification, caused largely by excessive CO2 emissions. Last year, researchers found that rising temperatures forced some bee species from their southernmost borders. The global range of cockroaches, Schal says, could also be affected by climate change.

“I think what’s more important with climate change is that some species with a southern distribution will be moving north,” Schal says. “The Asian cockroach invaded the US in 1986. South Carolina was as far north as it would go. But recently, we found it in North Carolina. I wouldn’t be surprised if, due to climate change, it makes its way farther north into Virginia, Maryland, Delaware … maybe even New York.”