Zoology

Behaviour Ecology Grasshoppers Locusts



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Grasshoppers and locusts belong to the insect order Orthoptera, which means leather-winged. These insects have incomplete life cycles, leathery forewings, membranous hindwings and chewing mouthparts. The Order includes four families. The family Acrididae includes the short horned grasshoppers and the true locusts. The other three families are the long horned grasshoppers and katydids (Stenopelmatidae and Tettigoniidae), and the crickets (Gryllidae).

Grasshoppers have another escape mechanism as well as their wings. They have long hind limbs used for jumping and this gives them their characteristic appearance. Grasshoppers and locusts are herbivores, grazing on grasses and foliage on shrubs and trees. They are tasty, nutritious and a desirable food to many insectivorous birds, mammals and reptiles. There are also invertebrate predators of grasshoppers plus parasites, so grasshoppers do have to be alert and quick. Many are also cryptically coloured. There are green grasshoppers hiding in grass and mottled brown grasshoppers that hide in leaf litter or on bark. Some grasshoppers have even become vaguely leaf shaped to help them hide.

Grasshoppers start as eggs of course and when they hatch, they look like tiny versions of the adult forms but wingless. They must eat until they outgrow their exoskeletons, then moult and grow a new and larger exoskeleton. As they grow, their wings begin to form until in their last moult, they achieve flight. Most species overwinter as eggs, with the eggs being laid in the ground by the females before they die.

One of the most interesting things about grasshoppers is their ability to 'sing'. The proper term is stridulation as the songs are produced by rubbing one body part against another. The males do the singing, presumably to advertise their fitness to females and to seduce them. Grasshoppers have to have auditory organs as well in order to hear the singing. These are oval eardrums located on the sides of the first abdominal segment or on the front legs. Species can be identified by the particular songs that they sing. The tempo of the song tends to increase as the day warms up as well.

Locusts are short horned grasshoppers in the swarming phase of their life cycle. During poor years, grasshoppers remain relatively harmless, but in good years with lots of food, populations soar and then form large swarms which fly across the landscape, consuming much of the vegetation in their path. Locust swarms can number in the millions and can wipe out crops, causing famine in places like Africa. However it is important to realise that locust swarms are not just plagues but naturally occuring phenomena that are a regular part of many ecosystems. Humans tend to react to locusts with dangerous chemical sprays which may actually do more harm to the environment than the locusts themselves.

Grasshoppers and locusts may harm agricultural crops but they are also important food sources for meny animals. Even humans have been known to eat them. They are also interesting animals in their own right and can provide a great deal of entertainment for children. When I have birds in care, I often send visiting children out to catch grasshoppers for me to feed the birds. Children are amazed at how quick grasshoppers are and how hard to catch, but after all, it is a life or death matter for the insects, whereas it is only a game for the kids.

Sources: http://www.thefreedictionary.com/Orthoptera

Borror and DeLong 1971 An Introduction to the Study of Insects

www.savethelocust.com

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