About locusts

Australian plague locusts can be identified by their scarlet hind legs and the distinctive dark spot on their hind wings.
http://www.daff.gov.au/animal-plant-health/locusts/about/australia

Locusts are flying insects that are related to, look, and often act like grasshoppers.  Three species of native locust cause widespread devastation in Australia: the spur throated locust, the migratory locust, and - most common of all - the Australian plague locust.

BEHAVIOUR
Locusts have two definitive behaviours: solitary and gregarious.  When population density is low, locusts are repelled by one another and behave as independent organisms - like common grasshoppers.  However when population density is high, locusts undergo physiological changes (like changing colour and body length) to transform into a gregarious state. 

WHY THE TRANSFORMATION?
Locusts become gregarious when they are forced into close proximity and jostle against each other.  This can be due to:
  • mothers laying eggs in dense quantities
  • limited food supplies forcing them into a small area to survive
The contact stimulates sense organs in the their hind legs which release neurochemical seretonin into the locust's central nervous system.  The seratonin acts on the neural circuit causing locusts to be attracted to each other.

SWARMING
It is in their gregarious state that locusts march and, when they grow wings, swarm.    Each locust can eat its weight in plant matter in one day, but in such large numbers they face a severe food shortage and become cannabilistic.  If one locust stops it is in danger of being eaten, and so they are all forced onwards.

Locust swarms can cover up to 50 km² causing devastation to crops and orchards.

MIGRATION
Locusts take flight every day at sunset and have been known to travel up to 500km overnight if weather conditions are right.

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