page_title: Grasshopper
section_title: Swarming
hierarchical_section_title: Grasshopper / Biology / Swarming
caption_attribution_description: English: Most commonly called grasshoppers, species in the family Acrididae vary greatly in shape, size and colouring, but all possess large hind legs well developed for jumping. They have short antennae, a short ovipositor and well-developed wings. Grasshoppers are active during the day and can produce sound by rubbing a row of pegs located on the hind legs against part of the forewings. Most species feed on grass (as their name suggest), but other vegetation is also consumed including leaves, stems and even dead eucalyptus leaves. The name locust is given to those species that are known to build up in large numbers. Locust swarms then migrate across vast areas causing almost complete destruction to all green vegetation, especially agricultural crops. The Australian plague locust is a native species of Australia and is one of the most economically important species in Australia. At times this species is known to build up in great numbers forming swarms that migrate across central and eastern Australia eating their way through almost anything green. This species can be recognised by the black patch on the tip of the hind wing and the red colouring on its hind leg. The body of female Australian plague locusts is usually green, but when swarming is brownish in colour.
context_page_description: Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is probably the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago.
  Grasshoppers are typically ground-dwelling insects with powerful hind legs which allow them to escape from threats by leaping vigorously. As hemimetabolous insects, they do not undergo complete metamorphosis; they hatch from an egg into a nymph or "hopper" which undergoes five moults, becoming more similar to the adult insect at each developmental stage. At high population densities and under certain environmental conditions, some grasshopper species can change color and behavior and form swarms. Under these circumstances, they are known as locusts.
  Grasshoppers are plant-eaters, with a few species at times becoming serious pests of cereals, vegetables and pasture, especially when they swarm in their millions as locusts and destroy crops over wide areas.
context_section_description: Locusts are the swarming phase of certain species of short-horned grasshoppers in the family Acrididae. Swarming behaviour is a response to overcrowding. Increased tactile stimulation of the hind legs causes an increase in levels of serotonin. This causes the grasshopper to change colour, feed more and breed faster. The transformation of a solitary individual into a swarming one is induced by several contacts per minute over a short period.
  Following this transformation, under suitable conditions dense nomadic bands of flightless nymphs known as "hoppers" can occur, producing pheromones which attract the insects to each other. With several generations in a year, the locust population can build up from localised groups into vast accumulations of flying insects known as plagues, devouring all the vegetation they encounter. The largest recorded locust swarm was one formed by the now-extinct Rocky Mountain locust in 1875; the swarm was 1,800 miles (2,900 km) long and 110 miles (180 km) wide, and one estimate puts the number of locusts involved at 3.5 trillion.
  An adult desert locust can eat about 2 g (0.1 oz) of plant material each day, so the billions of insects in a large swarm can be very destructive, stripping all the foliage from plants in an affected area and consuming stems, flowers, fruits, seeds and bark.
caption: Millions of plague locusts on the move in Australia
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