A plague of locusts

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by Kate C
Publish date
7 December 2010
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You've probably heard reports that northern Victorian farmers are losing whole crops to armies of marching hoppers and that locusts are on their way into Melbourne. The species in question is the Australian Plague Locust, Chortoicetes terminifera, which belongs to the short-horned grasshoppers (family Acrididae). High rainfall over past months has created a bounty of lush green growth for the locusts to eat, allowing them to breed to plague conditions.

‘Locust’ is used to describe grasshoppers that can swarm in huge numbers. Most grasshoppers are solitary and the Australian Plague Locust generally shuns company too. But something interesting happens when their numbers build up: they enter what is known as a gregarious phase and their behaviour changes profoundly.

Juvenile locusts aggregate in ‘hopper bands’ that march across pasture, devouring everything in their wake. The adults travel vast distances in flying swarms that can be kilometres wide. A swarm that covers just one square kilometre can eat ten tonnes of vegetation in one day.

locust swarm Band of nymphs moving through pasture, as seen from the air.
Source: Museum Victoria
 

We spotted locusts on a recent trip to Benalla; they were all over the town, hopping and flying over roads and gardens in low numbers.

locust This locust was sunning itself on the footpath of the main street in Benalla.
Image: Nicole Alley
Source: Museum Victoria
 

In some species – such as the Desert Locust found in Africa, the Middle East and Asia – the gregarious phase displays very different colours and body form to the solitary phase. Not so with the Australian Plague Locust; the two phases look pretty similar, especially when they’re dry specimens and their colours have faded, such as those in our entomology collection.

pinned grasshoppers Plague locusts in the Museum Victoria Entomology Collection.
Source: Museum Victoria
 

Links:

Australian Plague Locust Commission

DPI Victoria locust information

DPI NSW locust image gallery

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