Why grasshoppers migrate

They can stay in the air for long periods, regularly taking nonstop trips across the Red Sea. In , a swarm flew from northwest Africa to Great Britain, while in , another made the lengthy trek from West Africa to the Caribbean, a trip of more than 3, miles in just 10 days.

Locust swarms devastate crops and cause major agricultural damage, which can lead to famine and starvation. Locusts occur in many parts of the world, but today locusts are most destructive in subsistence farming regions of Africa. The desert locust Schistocerca gregaria is a notorious species.

Found in Africa, the Middle East, and Asia, this species inhabits an area of about six million square miles, or 30 countries, during a quiet period. During a plague, when large swarms descend upon a region, however, these locusts can spread out across some 60 countries and cover a fifth of Earth's land surface.

Desert locust plagues threaten the economic livelihood of a tenth of humans. A desert locust swarm can be square miles in size and pack between 40 and 80 million locusts into less than half a square mile. Each locust can eat its weight in plants each day, so a swarm of such size would eat million pounds of plants every day.

To put it into context, a swarm the size of Paris can eat the same amount of food in one day as half the population of France. But experts can look at past weather patterns and historical records to identify the areas where swarms might occur and spray those areas with chemicals.

Some experts worry that locust plagues will worsen in a warming world. Rising sea temperatures are causing prolonged bouts of wet weather, including a surge of rare cyclones in eastern Africa and the Arabian Peninsula where desert locusts thrive.

All rights reserved. Common Name: Locusts. Scientific Name: Acrididae. All of these sources of outbreaks make the migratory grasshopper a prime candidate for integrated pest management. Suggested methods of control include combining clean culture weed-free of crops, elimination of weedy fence rows and roadside strips, judicious use of herbicides and insecticides, planting thick stands of grasses in idle cropland, restoring grasses in depleted rangeland, protecting healthy rangeland from overuse, and annual monitoring of habitats and populations of the migratory grasshopper.

The migratory grasshopper, a mixed feeder of grasses and forbs, is a serious pest of both crops and grasslands. It causes more crop damage than any other species of grasshopper in the United States. High densities damage and may even destroy fields of wheat, barley, oats, alfalfa, clover, corn, vegetables, and ornamentals.

It also attacks vines, bushes, and trees, feeding on foliage, fruit, and bark. Populations that irrupt on weedy rangeland and in idle cropland may migrate in massive swarms to infest land miles away.

After flight, the migrants may number from per square yard, wreaking havoc on the vegetation of the landing area - rangeland, crops, or urban gardens.

Small grains are especially vulnerable to depredations of the migratory grasshopper. Losses of a wheat crop may occur in several ways. An early hatch of grasshoppers may completely destroy newly germinated seedlings of spring wheat. This occurs when the grasshoppers invade the crop from heavily infested stubble or roadside. Grasshoppers may also hatch within the field of growing plants when the crop is seeded in infested stubble. Gradual defoliation through the growing season reduces yield and quality of the wheat by depressing weight of the kernels.

Toward the end of the season, defoliated plants become susceptible to head clipping by grasshoppers, further decreasing yield. The grasshoppers feed on green areas of the stem close to the head, causing the head to fall to the ground.

A fourth way in which the migratory grasshopper damages wheat is the invasion in late summer of second generation nymphs and adults into the edges of newly emerged winter wheat. The grasshoppers consume the young plants to ground level. Row after row of seedlings are killed as the grasshoppers eat their way from the edge toward the center of a strip or field. This sort of damage occurs in western Kansas and surrounding regions where strip cropping of winter wheat is practiced.

Dispersal of a light infestation of one grasshopper per square yard in a fallow strip of wheat stubble to an adjoining field margin of young growing wheat concentrates the infestation to 55 grasshoppers per square yard.

High densities of the migratory grasshopper infesting rangeland seriously deplete forage for both livestock and wildlife. The grasshoppers not only feed on native forbs and introduced weeds but also on valuable forage grasses. In the desert prairie of Arizona where this species frequently reaches outbreak numbers, the grasshoppers damage blue grama, curly mesquite, red sprangletop, squirreltail, and stinkgrass as well as a variety of forbs and weeds.

In the mixedgrass prairie the migratory grasshopper attacks several native grasses including blue grama, western wheatgrass, bluegrasses, and sand dropseed.

A severe outbreak of the migratory grasshopper occurred in the mixedgrass prairie of South Dakota from through and an unusual but severe outbreak occurred in the bunchgrass prairie of British Columbia during In the latter case populations destroyed 70 to 80 percent of grasses on the open range. Much variation in size of the migratory grasshopper exists among specimens taken from different habitats and regions.

Live weights of males collected from a ranch roadside in eastern Wyoming averaged mg and of females mg dry weights mg and mg, respectively. Examinations of gut contents show that the migratory grasshopper is usually feeding on several species of plants growing in its habitat. This behavior is important in its ecology because laboratory studies have demonstrated that a mixed diet affords individual grasshoppers better nutrition. Although polyphagous, the migratory grasshopper selects host plants from its habitat.

Preferred foods include dandelion, tumble mustard, wild mustard, pepperweed, western ragweed, downy brome, Kentucky bluegrass, barley, and wheat. Nymphs and adults ingest dry materials lying on the ground surface including plant litter, cattle manure, and bran flakes.

The migratory grasshopper, as the common name implies, often disperses and migrates. Many accounts of adults swarming have been published, although there are few records of nymphal migration and still fewer accounts of adult migration in the absence of mass swarming.

Recent research has revealed that migratory behavior is inherent and regularly displayed, although considerable variability occurs among populations. The greatest degree of migration has been found in populations inhabiting areas where resources are patchy and unpredictable, as in Arizona and New Mexico. The least degree of migratory behavior was detected in a population inhabiting a relatively lush and stable environment in Colorado.

The older nymphs, third to sixth instars, may migrate as far as 10 miles but usually the distance is less than 5 miles. The nymphs travel together in a band at rates of around 0. Ask a Question. Keep the conversation going. Ask a follow up question to an article, ask something new, or give us your feedback.

Skip to content. Was this article helpful? Let us know if you liked the post. Related Articles Grasshoppers Migrating? Grasshoppers appear to be migrating into canola fields to feed on pods in the drier parts of southwestern Manitoba and eastern Saskatchewan. This natural system of " collective motion ," which spells doom for a crop, is also common among ants, birds and fish.

Live Science. Remy Melina.