Page 118 - The Miracle of Migration in Animals

THE MIRACLE OF MIGRATION IN ANIMALS

The Crucial Factor in Locust Migration

At present, we do not know exactly what causes a locust to

move into the gregarious phase, although researchers say that an in-
crease in population density triggers the process. Various laboratory
experiments show that an area on the locusts’ hind legs plays an ef-
fective role. Professor Stephen Simpson of University of Oxford re-
vealed that the crucial point that sets off the transition to the
gregarious phase is the femur region.
On examination, a locust’s body reveals the wonder of the cre-
ation. A large area of the locust’s integument is covered with touch-
sensitive hairs and other mechanoreceptors. The hairs in the thigh
region, which play an important role in inducing gregarization, are
stimulated by touch.
The transition to the gregarious phase, which initiates locust mi-
grations, occurs more often where there is an irregular distribution of
food. In a region where vegetation is spotty, locusts in the area start
grouping together to feed. In this way, they come into close contact
with one another, and their transition to the gregarious phase begins.

Locust migration is affected by climatic conditions, the seasons
and rainfall, for to breed and lay their eggs, they need to be in rainy
regions. In some species, females lay their eggs immediately after it
rains and the ground is soft. Some species do lay their eggs on dry
ground, but the young do not emerge until it rains—a precaution that
ensures a food supply for the newly-hatched locusts. Swarms of lo-
custs move with the wind, which carries them to regions where
there’s a possibility of rainfall, which will give them the opportunity
to breed.
Of all the species, desert locust—found in Central and North
Africa down to Tanzania, the Middle East, Pakistan and India—is the
most widespread and the most destructive.

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