Most grasshoppers lead relatively blameless
lives, causing little harm to crops or gardens. However, some species of grasshoppers lead a 'Jekyll and Hyde' existence and can change into a very damaging form.
congregate in huge swarms that can do severe damage to crops. These swarming grasshoppers are
called locusts. There are more than 20,000 species of grasshoppers known to science, but only
about a dozen of these transform into locust and produce damaging swarms.
Locusts have two 'phases' of existence. When food is plentiful, they
exist in the solitary form. In this form they act just like other grasshoppers - they have no
tendency to form swarms and they do little damage. Locusts can exist in the solitary form for many
generations. However, if food becomes scarce, they change into a totally different form, this form
of locust is called the 'gregarious locusts' - following the transformation you would not think
they were the same species.
However, it is not just the appearance change which is the problem,
it is the change in behaviour. When locusts change into this new form they really like each others
company, they join together in an enormous swarm (we are talking billions of locusts, covering hundreds
of square miles in the worst cases) and eat just about every green thing they encounter. Swarms can travel
vast distances covering 130 kilometres per day.
The female lays her eggs directly into the soil.
After two weeks, a solitary green locust (grasshopper) emerges.
When food supplies are scarce, they interact with other solitary grasshoppers and turn into a locust - changing colour from green to yellow and black.
The locusts which are called 'gregarious' locusts form a swarm and attack crops.
It is recorded that one particular swarm in 1988 covered an
area of 75 x 15 miles in North West Africa. The swarm contained about 150 billion locusts and was
estimated to be eating 300,000 tons of fresh green food per day.
If you have ever wondered how a grasshopper can cover so much
ground and do so much damage, just consider the insects eyes.
Located on the head, along with
antennae and chewing mouth parts, are two kinds of eyes.
The large 'compound' eyes consist of thousands of little eyes that work together to form a single picture in the grasshoppers brain. If you have ever tried to catch a grasshopper, you know how difficult it can be. That is because these eyes enable the insect to see forward, backward and sideways for long distances. Grasshoppers also have three small single eyes.
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