...if any get loose, they're going to have a serious infestation problem-- they will literally take over an area.
Illustration by Paul M. Breeden, National Geographic
Published October 7, 2013
Move over, Sharks and Jets. New Yawk's next turf rumble could pit roach against roach.
According to an ongoing study called the National Cockroach Project, the roaches of three NYC neighborhoods—the Upper West Side, the Upper East Side, and Roosevelt Island—are genetically distinct. Like many of the city's humans, each group tends to stay in its own neighborhood. And, since American cockroaches originated overseas, these urban insects can also claim immigrants as ancestors.
To find out more about what's bugging the Big Apple, we sat down with the project's lead scientist: Mark Stoeckle, an infectious-disease specialist and senior research associate at the Rockefeller University's Program for the Human Environment.
How did the National Cockroach Project come about?
We'd been working with high-school students using bar coding, which is a simple way of identifying species by DNA. And one of the projects a couple of years ago was a sort of CSI for the home—students went around and collected everything they could find that might have DNA in it. When we had that tested, one of the things that turned up was a cockroach that looked genetically distinct.
We thought we might have a new species, but when we had it looked at in the American Museum of Natural History, they said, "No, that's a regular American cockroach." So [to understand why it seemed genetically distinct] we needed a lot more specimens.
The idea became to involve students and other citizen scientists to help us collect cockroaches. There hadn't been a lot of work done on them, because they're pests. So this [is an opportunity] to learn about something that lives in cities, where most of us live.
So how does it work—students and other citizen scientists collect cockroaches and send them to you?
Yes. At first we weren't sure if anyone would actually send in a cockroach—it's certainly an unusual request—and we weren't sure what condition it would arrive in. Cockroaches are icky, but they're not dangerous like, say, ticks, which can actually carry blood-borne diseases.
You're saying roaches don't deserve the bad rap they get?
I mean, I don't like seeing them crawling across my floor. They can track things in—they're sort of like houseflies in that way. And they may contribute to allergies, particularly asthma; the dust from cockroach shells may be an issue. But they don't carry specific diseases.
How many samples have you received so far, and from where?
We've gotten about 200 specimens, either mailed in or [hand-delivered]. Most are from the U.S., from New York City. We've had better luck getting New Yorkers to pick up cockroaches than we've had elsewhere.
But we also have specimens from Australia and Spain. Two high-school students in Spain saw our project on the Web and sent them in. It's really wonderful that people we have no direct connection to are interested and willing to contribute.
How many species of roaches are there in the world?
More than 4,000. Most live out in the wild. A few of them have adapted—or already were adapted—to a human environment. The common ones that are considered pests in the United States are the American cockroach (the large, water-bug type) and the German cockroach (the smaller one more common in apartments or households). Those are the two main ones. There's also the smokybrown cockroach and the brown-banded cockroach.
So how are roaches like New Yorkers?
Well, they're definitely immigrants. We know these are tropical species that are thought to have come from Africa, though there's no definite proof of that. They require a very warm, moist environment. And we've made a nice home for them in cities, because we have underground tunnels and sewers where they can live year-round. In the summer they come up above ground, and that's when we usually see them. But they've only been here as long as we've had an underground environment that's congenial for them.
So they're all immigrants and like New Yorkers in that way. The other way—the biggest finding of the study—is that there are four distinct genetic types of cockroaches within this species [the American cockroach]. Evolutionarily these genetic types are separated by a million or two million years. So they were probably living in different parts of the world. We brought them here.
They do interbreed, so we don't think they're separate species. But on the other hand, in the New York City neighborhoods where we've looked in detail—the Upper West Side, the Upper East Side, and Roosevelt Island—the genetic types are quite different. So they must be staying close to home.
The diversity was a surprise to us, and the fact that they're not just all mixed together—it's not a random assortment. So they must be staying close to home, and they have their own neighborhoods.
Do the genetic differences in neighborhood roaches manifest themselves in terms of behavior, appearance, longevity? What about vulnerability to pesticides?
It's possible. We just haven't looked at that. Cockroaches look all the same to us, but presumably they can tell each other apart. They are social insects, like ants. They don't have as elaborate a society as ants. But they do definitely live in groups.
For our citizen-science project we're probably not going to be studying pesticide resistance. But [we've created an] opening for someone to look at that.
What would happen if you took an Upper West Side roach and relocated it to, say, the Lower East Side?
Ha, I don't know. Maybe we can do some tracking experiments—put tiny radio collars, very little cameras on them. It's a fun question to think about and guess what might happen.
What can we learn from this project?
There's a lot more diversity going on around us than we might realize. We think of an urban environment as a boring environment for wildlife. But in fact, at least with this one species, there's a lot going on there. That's one part of it.
The other part is that they're all immigrants, like all New Yorkers—they've come here from different parts of the world.
So what do you do if you see a roach in your apartment?
I step on it. And I carry a plastic bag with me so I can pick it up and stick it in the freezer. I have a freezer in my apartment with a lot of cockroaches in it.
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