EXPLAINER: What is the Difference between Locusts and Grasshoppers?

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Agriculture CS Mwangi Kiunjuri on Friday morning while on a presser at Kilimo house asked Kenyans to take photos of insects they suspect to be locusts and share on social media for his ministry to advise whether they are real locusts or just insects that can do no harm.

“If you see any insect that you suspect could be a locust, take a picture and post on social media so we can confirm for you what insect it really is,” he said.


So, how to know a real locust?

According to The Food and Agriculture Organization of the United Nations (F.OA), Locusts are part of a large group of insects commonly called grasshoppers which have big hind legs for jumping. Locusts belong to the family called Acrididae. Locusts differ from grasshoppers in that they have the ability to change their behaviour and habits and can migrate over large distances.

Locusts and grasshoppers are the same in appearance, but locusts can exist in two different behavioural states (solitary and gregarious), whereas most grasshoppers do not. When the population density is low, locusts behave as individuals, much like grasshoppers. However, when locust population density is high, individuals undergo physiological and behavioural changes, known as phase polyphenism, and they form gregariously behaving bands of nymphs or swarms of adults.

In addition to changes in behaviour, phase change may be accompanied by changes in body shape and colour, and in fertility, physiology and survival. These changes are so dramatic in some species that the swarming and non-swarming forms were once considered to be different species.  The scale of population increase and migrations also distinguish those species known as locusts from grasshoppers.

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The distinction between locusts and grasshoppers is often not clear-cut, as the extent to which different species exhibit gregarious phase characters is graded. The migratory locust has all of the features associated with phase change – differences in body shape and colour, fertility and gregarious behaviour in both the nymph and adult life stages, forming dense bands and swarms. The Australian plague locust also forms dense nymph bands and adult swarms, but does not exhibit changes in body colour. Spur-throated locust nymphs do not form bands and the adults do not lay eggs gregariously, but they do form dense swarms.

Some species that are called grasshoppers, such as Austroicetes cruciataOedaleus australis and Peakesia spp. can form loose swarms at high densities, but do not generally migrate long distances as locusts do.

Identifying male and female locusts

Adult male and female locusts are readily distinguished by the shape of the tip of the abdomen; The end of the abdomen of the male locust is rounded due to the sub-genital plate which conceals the reproductive organs. The end of the abdomen of the female locust appears pointed due to the upper and lower jaws of the ovipositor.

[Photo: Courtesy]
On average, adult male locusts are smaller than adult females of the same species. However, size is not a reliable character to determine the sex of a locust as it varies according to the quality and abundance of food during the nymph stage.

Desert Locust females lay eggs in an egg pod primarily in sandy soils at a depth of 10-15 centimetres below the surface. A solitary female lays about 95-158 eggs whereas a gregarious female lays usually less than 80 eggs in an egg pod. Females can lay at least three times in their lifetime usually at intervals of about 6-11 days. Up to 1,000 egg pods have been found in one square metre.

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Source: F.O.A, Agriculture.gov.au

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