Grasshoppers, locusts and crickets - Orthoptera

Fast facts about grasshoppers and crickets

  • Over 24 000 species worldwide, mainly in the tropics, around 1000 in Europe, just 33 in the UK, and most of these in the south, 7 in Scotland.
  • Medium to large insects with a stout body.
  • Body lengths range from 5 - 120 mm.
  • The hind legs are usually enlarged and modified for jumping.
  • Usually 2 pairs of wings in the adult with the front pair tough and leathery and called tegmina.
  • Biting, chewing mouthparts.
  • Hemimetabolous, i.e. the young resemble the adults.
  • Adult males and females are very easy to tell apart as the females have visible ovipositors, and the males a pair of claspers to hold the female while mating.
    When the eggs hatch the young are worm-like, but soon moult into the juvenile form.
  • In colder climates most adults die before winter and after laying eggs. Only the eggs can survive the winter cold.
  • Adults can stridulate (produce a sound by rubbing body parts together). Grasshoppers rub their hind legs against their wings, and crickets rub their wings to stridulate.
  • Both sexes can stridulate, but it is mainly the males who do so.
  • The "ears" of grasshoppers are at the base of their abdomen (nearest the thorax), and crickets have their "ears" on their front legs.
  • Grasshopper fossils first appear in the Upper Carboniferous.
  • Easy to keep as pets.
  • If humans were as good as Orthoptera at jumping we would jump over 90 m in height and 150 m in length!

House cricket, Acheta domesticus

On the left is a juvenile house cricket, Acheta domesticus, in the family Gryllidae. It is found in buildings, rubbish dumps and sold as live pet food for lizards, etc. It is not native to the UK, and arrived from North Africa and the Middle East in the 17th century.

Note the antennae, I could not include the entire length in the photograph, but they are filiform and longer than the entire body. This is a rather young juvenile, so there is no sign of wings yet. These will appear larger with each moult until they are fully formed in the final moult. The wings are functional in both sexes. A fully grown specimen is 14 - 20 mm long. Note the two cerci sticking out of the rear, these are very sensitive to air movements.

It is an omnivorous scavenger, and although it does not eat wool, cotton, leather and wood it can damage them by its constant nibbling action. It is not active in the cold, so in the UK it is found indoors in colder months, or in compost heaps and rubbish dumps where the fermenting and decaying provides warmth.

The male makes the shrill chirping noise by rubbing the serrated edges of his forewings together. Only the males produce the sound, and the females hear the sound with hearing organs on their legs.

Both adults and nymphs will die if starved for 1 week.

The female can lay several hundred eggs, usually in batches, in cracks, crevices or soft soil. The eggs are whitish-yellow, about 2.5 mm long and 0.5 mm wide. They hatch in around 2 - 3 months, but this varies greatly with temperature. The nymphs take around 6 months to mature, but again this varies greatly with temperature.

field cricket, Gryllus campestris

The Great green bush cricket, Tettigonia viridissima

On the right is the Great green bush cricket, Tettigonia viridissima. It is in the Tettigoniidae family which contains all the bush crickets and katydids. They are found in southern England, and along the south coast of Wales. This one was photographed in the Dordogne in France.

Adults tend to make short, hopping flights when disturbed, and sometimes don't even bother to fly, they just walk away.

Stridulation is by rubbing the wings together. Their food is other insects. Eggs are laid in the soil where they overwinter and hatch the following spring.

Great green bush cricket, Tettigonia viridissima
Oak bush cricket Meconema thalassinum

Oak bush cricket, Meconema thalassinum

On the left is the oak bush cricket, Meconema thalassinum. This is a female, note the curved ovipositor she will use to lay her eggs under the bark of deciduous trees. A fully grown one will be 13 - 17 mm long, with an ovipositor 8 - 9 mm long. Nymphs are seen from May - August, and adults from August - October.

Both sexes have functional wings at maturity. Though she is called the oak bush cricket, these crickets can be found in a variety of habitats, and are commonly found in lighted rooms at night, though they are weak fliers. In England they are found in or near woodlands, where they are active after dark from around August to November.

The antennae are much longer than the body and are filiform and whip-like. This species is unusual in that unlike most other species the males can stridulate (make a noise by rubbing body parts together) only very weakly by rubbing the forewings. However males do generate sound by "drumming" with one hind leg on a leaf to attract females. They feed on small insects and are active predators.

Mole cricket, Gryllotalpa gryllotalpa

Right is the mole cricket, Gryllotalpa gryllotalpa, in the family Gryllotalpidae. There are 60 species in the world, but only one species in northern Europe, and it is 35 - 46 mm long, and is light chestnut coloured with velvety hairs. In the UK it is a protected species and is found in just a few locations in southern England.

mole cricket, Gryllotalpa gryllotalpa

Mole crickets are usually found in damp ground near ponds, streams or lakes. Adults burrow in the ground making extensive tunnels just below the surface. Note the front legs are strongly toothed and modified for digging, and they use their rear legs to push back the soil.

The eggs are laid in a chamber just below the surface too, so they can benefit from the heat of the sun. Unlike most other crickets the female has no external ovipositor. She lays 200 - 300 eggs, and guards and tends the young.

The young hatch in 2 - 3 weeks and leave the nest to fend for themselves about a month later.

Adults and young eat plant roots and insect grubs. Mole crickets in great numbers are considered a pest, but as they eat many pest grubs themselves, they may do more good than harm. The nymphs go through about 10 moults which takes 1 - 2 years to complete. Males stridulate like other crickets by rubbing their forewings together. The southern European mole cricket male, Gryllotalpa vinea, digs special burrows with two funnel-shaped openings to amplify his singing, which can be heard 500 m away. In adults the hind wings are fully developed, but their flight is clumsy.

On the right is a grasshopper head giving the names of the mouthparts etc.

Differences between grasshoppers and crickets

Feature Grasshoppers Crickets
Antennae Short, relatively thick Long and thin
Hearing Organs located each side of abdomen near where it joins the thorax On the hindmost leg

grasshopper head diagram

Locust

Locust

On the left is a locust. Locusts are just large grasshoppers that are strong fliers. Locusts tend to live their lives in what is known as the "solitary phase". What this means is that they live alone and tend to hop away from other locusts when they come into contact with them. However at times when there is a large population of locusts these contacts become more frequent, and it is then that the locust can enter into what is called the "gregarious phase".

During this phase they tend to crowd together and act as a swarm. Once they become adults they can fly, and will fly off as a swarm to find food, land and eat until there is no more food, then fly off and repeat the process. The gregarious phase occurs in years when there are a large number of eggs in the soil and the environmental factors, temperature, moisture, etc. are right to allow a large percentage of those eggs to hatch and survive. The female lays eggs in pods of around 120 eggs., and each female can lay about 5 pods, so around 500 eggs in all.

The locust and Volvo cars

Locust swarms number millions of densely packed insects flying at speed. So how do they avoid collisions? Well, they have special neurons in their brains to detect any rapidly approaching object (predator or other locust). This system has been studied and used by Volvo to help them design a collision avoidance system for their cars.

Desert locust, Schistocerca gregaria

On the right is a preserved specimen of the desert locust, Schistocerca gregaria.

In the Plain of Seldon in northern Nigeria a swarm of locusts settled and fed for four hours. When they left there was no vegetation over an area measuring 25 x 5 km, and that same area was covered with a layer of excrement 2 cm deep.

As the locusts arrived they blotted out the sun and made a noise that the locals described as being like that of a large waterfall. Their weight was so great that they broke branches off trees, and the noise of their eating was like the sound of a bush fire.

Schistocerca gregaria, the desert locust

A swarm can contain 50 billion individuals capable of eating 100 000 tonnes of vegetation per day. In a bad year locust swarms can cover a fifth of the Earth's land surface.

Locust flight speed has been recorded as 4.4metres per second. Compare this with other insects.

 
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