Why do grasshoppers swarm

On July 24, Tokyo decided to strengthen its position in terms of its invasion of China by moving through Southeast Asia. Raised in a middle-class English family, Michael Philip Jagger attended the London School of Economics but left without graduating in order to pursue On July 26, , Ed Gein, a serial killer infamous for skinning human corpses, dies of complications from cancer in a Wisconsin prison at age Truman signs the National Security Act, which becomes one of the most important pieces of Cold War legislation.

The act established much of the bureaucratic framework for foreign policymaking for the next plus years of the Cold War. By July , the Cold On July 26, , Confederate cavalry leader John Hunt Morgan and of his men are captured at Salineville, Ohio, during a spectacular raid on the North. Starting in July , Morgan made four major raids on Northern or Northern-held territory over the course of a year.

The U. CART later known as Live TV. This Day In History. History Vault. Locusts are actually special kinds of grasshoppers known for their gregariousness, and not in a good way. Normally solitarious a word that locust biologists made up, by the way , they change color and grow bigger muscles as they gather into massive clouds, rolling across landscapes and devastating crops.

Jekyll and Mr. The kind of desert locust currently plaguing East Africa is in fact named for this tendency to socialize: Schistocerca gregaria. But why does the desert locust go gregarious, when the vast majority of grasshopper species remain solitarious? That might have something to do with the dry environments these species call home. Desert locusts only lay eggs in moist soil, to keep them from drying out. When heavy rains come in to saturate the desert, locusts—ever the opportunists—breed like mad and fill the soil with their eggs, perhaps 1, per square meter of soil.

As soon as things start getting crowded, desert locusts become gregarious and migrate away in search of more food. Indeed, while solitarious locusts avoid eating toxic plants, the gregarious locusts are actually attracted to the odor of hyoscyamine, a toxic alkaloid found in local plants. But the conditions must be just right for locusts to join forces. Sudden rainfall, for example, could help feed a growing population and cause flooding that corrals locusts together and attract more locusts to join.

What starts as a small group can turn into a thrumming swarm of thousands, millions or even billions of locusts. As part of this transformation, locusts may change color, Song said.

Some species of locusts become migratory, flying long distances across borders in search of food. The most devastating, best-known, and most frequently studied example is the desert locust Schistocerca gregaria. The enormous swarms of desert locusts can be utterly devastating for famers whose livelihoods depend solely on those crops, she said. There are about 20 species of locusts, and they all undergo a dramatic transformation when there are many other locusts of the same species nearby.

The locusts shift from what scientists call the solitarious, or solitary phase when the locust is alone, to the gregarious phase when they swarm together. The specific signal that instigates the phase shift varies from species to species, Song said. For example, although both species react to the sight and smell of other locusts in a laboratory setting, the desert locust can shift into the gregarious phase with a touch on the hind legs, whereas the sensitive area on the Australian plague locust Chortoicetes terminifera is its antennae, he explained.

These triggers seem to boost levels of serotonin, the same chemical associated with mood in humans. Related: Image gallery: Striking photos of locust swarms. The two "Jekyll and Hyde" versions of the locust are an example of a phenomenon called "phenotypic plasticity.

One theory to explain why locusts adapted to have such phase changes, according to Song, is that the switch is a response to a changing environment. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options.

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