For the third year in a row, skies over Madagascar are black with millions of locusts — the insects of biblical fame that gobble up crops and ravage landscapes, mostly in countries where people barely get by.

This swarm, of red locusts, has come together to breed and feed. In rural parts of Madagascar, the bugs are taking a huge toll on rice and maize. Last week, a heat wave drew them to the capital city of Antananrivo as well, making for an apocalyptic urban scene (see video).

That's no surprise to Iain Couzin , a Princeton University biologist who studies swarms. Madagascar saw a similar locust swarm last spring that shoulders partial blame for a 264-ton shortfall in the country's rice harvest in 2013. Couzin predicted that without a speedy and sustained response — and proper funding — the insects would be back with a vengeance.

The United Nations did fund an effort to coat nearly 2.5 million acres of farmland with insect-killing pesticides in September 2013. But the locusts returned.

We asked Couzin to share his knowledge of locust swarms — why they happen, how to stop them, why they're a big problem in the developing world — and whether chowing down on the critters might be a good way to deal with the excess.

Why is Madagascar so hard hit — and who's suffering as a result?

What we're likely seeing is the problem from last year compounded. We still don't really know all the factors involved in making them swarm, but certainly weather conditions and a changing climate have an effect. In 2013, massive flooding from a cyclone created a perfect breeding environment for the insects, for example.

These invasions are devastating in countries where people rely so heavily on crops. Subsistence farmers don't get a second chance to plant and grow what they need. Their livelihoods are destroyed, and people go hungry.

How big are the swarms, and how much of the world do they affect?

A single swarm may be an estimated 460 square miles in size, and there can be some 80 million locusts packed into less than a half-mile square. They wipe out massive areas and affect entire economies. The FAO [Food and Agriculture Organization of the United Nations] estimates that in Madagascar, about two-thirds of the landscape could be invaded and 13 million people's livelihoods are at risk from the current swarms.

Are there plants that seem immune to the swarms?

Sometimes locusts just march through [and do not eat] crops that seem to us to be perfectly delicious. We've discovered that the insects are often very short on protein and salt [so they seek out crops with these nutrients]. So it can be quite unpredictable what plants they're going to choose. Certainly, though, human-generated crops that have been fed and watered are particularly at risk.

Are there countries that have handled the swarms well? Why can't other countries follow suit?

There used to be big swarms near the Red Sea in Israel. But Israel and Egypt now have the technology to monitor them, to apply pesticides quickly where needed, etc. So it's now very rare to see problems in those countries.

The reason the swarms are so bad elsewhere is because they are compounded by other issues — civil war, famine, political unrest. In parts of Africa in particular, the political situation is very dynamic. Even relatively stable countries, like Morocco and Mauritania, struggle because they don't see eye to eye and don't help each other as much as they could.

What do we know about red locusts, the type flying over Madagascar right now?

Honestly, we know next to nothing about red locusts ! There was a lot of descriptive fieldwork on them in the 1950s, likely facilitated by the British army's presence in Africa. It's thought that they are similar to the desert locust, but nobody knows! Isn't it astonishing that so little can be known about such an economically important species, and one that impacts so many human lives? It always amazes me.

According to the U.N., the FAO began a $45 million pesticide campaign in Madagascar after the 2012 locust plague, but funding has stalled with many millions still needed.

When you have these massive swarms, it's really a wake-up call. You have to go in early and hard and be persistent. It's very much like the treatment of a disease: Early response is critical and must be sustained. There needs to be policy that supports the effort and funding not just to act but so scientists can study and really learn how the insects move over long distances. There's no money for that now, which is incredible when you think of both the economic and humanitarian costs of these plagues.

What do we know about locust behavior that helps explain why they swarm?

What we know about desert locusts [the most well-studied] likely applies to other types. Locusts don't like being together. At low density they are quite happy with a solitary lifestyle. When resources are abundant, their populations can grow, and then they are forced to come together as they deplete those resources. So, say, during a drought, they all aggregate together to feed. And that closeness changes their behavior. As they begin bumping into each other, they actually begin to cannibalize each other. Individuals are both trying to eat each other and avoid being eaten. So they form rolling bands that march across the landscape, eating.

Could technology help out?

Actually, the military can see these swarms from their satellites. As imaging and other technologies improve, I would love to use these tools to observe, to really monitor these flying swarms. It's a matter of putting the right people and technologies together. This isn't going to make anyone a bunch of money. But it could protect livelihoods and save millions of lives! As a society, it's our duty to pursue it.

We keep hearing that insects are an underutilized protein source. Should we encourage people suffering locust invasions to feast on them?

Actually, that would be terribly dangerous! Locusts sequester toxins from wild plants they eat in the environment. It's part of their evolutionary strategy for dealing with predators, to make themselves toxic. Even when just handling them, my hands swell up and crack from that exposure. A colleague of mine tried eating one, and his lymph nodes swelled up like golf balls in his neck. The toxins are very severe. When locusts are only eating crops, then they're probably fine and safe to eat. But when they have the chance, they will feed on the most toxic plants possible in the wild. Eating a lot of them could be fatal. So no, it's not something I'd recommend.

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