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Grasshopper
Fossil range: Late Permian - Recent
Immature grasshopper
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Order: Orthoptera
Suborder: Caelifera
Ander, 1939
Superfamilies
  • Tridactyloidea
  • Tetrigoidea
  • Eumastacoidea
  • Pneumoroidea
  • Pyrgomorphoidea
  • Acridoidea
  • Tanaoceroidea
  • Trigonopterygoidea

The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as short-horned grasshoppers. Species that change colour and behaviour at high population densities are called locusts.

Contents

Characteristics

A grasshopper uses camouflage to aid its survival
Grasshopper mouth structure

Grasshoppers have antennae that are almost always shorter than the body (sometimes filamentous), and short ovipositors. They also have pinchers or mandibles that cut and tear off food.[1] Those species that make easily heard noises usually do so by rubbing the hind femurs against the forewings or abdomen (stridulation), or by snapping the wings in flight. Tympana, if present, are on the sides of the first abdominal segment. The hind femora are typically long and strong, fitted for leaping. Generally they are winged, but hind wings are membranous while front wings (tegmina) are coriaceous and not fit for flight. Females are normally larger than males, with short ovipositors. Males have a single unpaired plate at the end of the abdomen. Females have two pairs of valves ( triangles) at the end of the abdomen used to dig in sand when egg laying.

They are easily confused with the other sub-order of Orthoptera, Ensifera, but are different in many aspects, such as the number of segments in their antennae and structure of the ovipositor, as well as the location of the tympana and modes of sound production. Ensiferans have antennae with at least 20-24 segments, and caeliferans have fewer. In evolutionary terms, the split between the Caelifera and the Ensifera is no more recent than the Permo-Triassic boundary (Zeuner 1939).

Diversity and range

Recent estimates (Kevan 1982; Günther, 1980, 1992; Otte 1994-1995; subsequent literature) indicate some 2,400 valid Caeliferan genera and about 11,000 valid species described to date. Many undescribed species exist, especially in tropical wet forests. The Caelifera are predominantly tropical.

Biology

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Digestion and excretion

The digestive system of insects includes a foregut (stomodaeum, the mouth region), a midgut (mesenteron), and a hindgut (proctodaeum, the anal region). The mouth leads to the muscular pharynx, and through the esophagus to the crop. This leads to the malpighian tubules. These are the chief excretion organs. The hindgut includes intestine parts (including the ileum and rectum), and exits through the anus. Most food is handled in the midgut, but some food residue as well as waste products from the malpighian tubules are managed in the hindgut. These waste products consist mainly of uric acid, urea and amino acids, and are normally converted into dry pellets before being disposed of.

The salivary glands and midgut secrete digestive enzymes. The midgut secretes protease, lipase, amylase, and invertase, among other enzymes. The particular ones secreted vary with the different diets of grasshoppers.

Nervous system

The grasshopper's nervous system is controlled by ganglia, loose groups of nerve cells which are found in most species more advanced than cnidarians. In grasshoppers, there are ganglia in each segment as well as a larger set in the head, which are considered the brain. There is also a neuropile in the centre, through which all ganglia channel signals. The sense organs (sensory neurons) are found near the exterior of the body and consist of tiny hairs (sensilla), which consist of one sense cell and one nerve fibre, which are each specially calibrated to respond to a certain stimulus. While the sensilla are found all over the body, they are most dense on the antennae, palps (part of the mouth), and cerci (near the posterior). Grasshoppers also have tympanal organs for sound reception. Both these and the sensilla are linked to the brain via the neuropile.

Romalea guttata grasshoppers mating
Common Macrotona (Macrotona australis) laying eggs

Reproduction

The grasshopper's reproductive system consists of the gonads, the ducts which carry sexual products to the exterior, and accessory glands. In males, the testes consist of a number of follicles which hold the spermatocytes as they mature and form packets of elongated spermatozoa.

During reproduction, the male grasshopper introduces sperm into the ovipositor through its aedeagus (reproductive organ), and inserts its spermatophore, a package containing the sperm, into the female's ovipositor. The sperm enters the eggs through fine canals called micropyles. The female then lays the fertilized egg pod, using her ovipositor and abdomen to insert the eggs about one to two inches underground, although they can also be laid in plant roots or even manure. The egg pod contains several dozens of tightly-packed eggs that look like thin rice grains. The eggs stay there through the winter, and hatch when the weather has warmed sufficiently. In temperate zones, many grasshoppers spend most of their life as eggs through the cooler months (up to 9 months) and the active states (young and adult grasshoppers) live only up to three months. The first nymph to hatch tunnels up through the ground, and the rest follow. Grasshoppers develop through stages and progressively get larger in body and wing size. This development is referred to as hemimetabolous or incomplete metamorphosis since the young are rather similar to the adult.

Six stages of development, from newly-hatched nymph to fully-winged adult. (Melanoplus sanguinipes)

Circulation and respiration

Grasshoppers have open circulatory systems, with most of the body fluid (haemolymph) filling body cavities and appendages. The one closed organ, the dorsal vessel, extends from the head through the thorax to the hind end. It is a continuous tube with two regions: the heart, which is restricted to the abdomen; and the aorta, which extends from the heart to the head through the thorax. Haemolymph is pumped forward from the hind end and the sides of the body through a series of valved chambers, each of which contains a pair of lateral openings (ostia). The haemolymph continues to the aorta and is discharged through the front of the head. Accessory pumps carry haemolymph through the wing veins and along the legs and antennae before it flows back to the abdomen. This haemolymph circulates nutrients through the body and carries metabolic wastes to the malphighian tubes to be excreted. Because it does not carry oxygen, grasshopper "blood" is green.

Respiration is performed using tracheae, air-filled tubes, which open at the surfaces of the thorax and abdomen through pairs of spiracles. The spiracle valves only open to allow oxygen and carbon dioxide exchange. The tracheoles, found at the end of the tracheal tubes, are insinuated between cells and carry oxygen throughout the body. (For more information on respiration, see Insect.)

Grasshopper from underneath

Diet

Diets of grasshopper species from two arid grassland communities in Trans-Pecos, Texas, were determined by gut analysis. Species-specific food plant choice and niche breadths are presented for each of these species. As a group, grasshoppers range from monophagous to polyphagous feeders although most species fall in the oligophagous to polyphagous group. Phylogenetic constraints are evident such that gomphocerinae are primarily grass feeders while melanoplinae feed predominantly on forbs; the oedipodinae show less clearcut tendencies. Feeding patterns are remarkably constant from site to site and overall, community niche breadth distributions between sites do not differ greatly. Individual species tend to eat the same plant species at various sites and maintain similar niche breadths. Species with relatively specialized diets tend to feed on predictable plant species such as grasses and long-lived perrenial forbs. Grasshopper feeding patterns present some problems to the current theory of herbivore diet specialization since forb feeding melanoplines tend to be polyphagous (contrary to predictions). Life history patterns unrelated to tracking host plants may explain some aspects of diet breadth since diet selectivities are presumably adjusted according to the probability of finding suitable food plants.

Other information

As food

In many places around the world, grasshoppers are eaten as a good source of protein. In Mexico for example, chapulines are used as a snack or filling. They are served on skewers in Chinese food markets, like the Donghuamen Night Market.[2]

Raw grasshoppers should be eaten with caution, as they may contain tapeworms.[3]

In some countries in Africa, grasshoppers are an important food source, as are other insects, adding proteins, fat, minerals, and vitamins to the daily diet, especially in times of food crisis. Grasshoppers are usually collected at dusk, using lamps or electric lighting, in sweep nets. They are placed in water for 24 hours, after which they can be boiled or eaten raw, sun-dried, fried, flavoured with onions, or used in soup. The "grasshoppers" eaten in Uganda and neighbouring areas are called nsenene, but they are in fact bush crickets, also called katydids.

In some countries in the Middle-east, grasshoppers are boiled in hot water with salt, left in the sun to dry then eaten as snacks.

Grasshoppers are kosher.

Locusts

See also locust and desert locust.

Locusts are several species of short-horned grasshoppers of the family Acrididae that sometimes form very large groups (swarms); these can be highly destructive and migrate in a more or less coordinated way. Thus, these grasshoppers have solitary and gregarious (swarm) phases. Locust swarms can cause massive damage to crops. Important locust species include Schistocerca gregaria and Locusta migratoria in Africa and the Middle East, and Schistocerca piceifrons in tropical Mexico and Central America (Mesoamerica). Other grasshoppers important as pests (which, unlike true locusts, do not change colour when they form swarms) include Melanoplus species (like M. bivittatus, M. femurrubrum and M. differentialis) and Camnula pellucida in North America; the Romalea guttata (Lubber Grasshopper), Brachystola magna, and Sphenarium purpurascens in northern and central Mexico; species of Rhammatocerus in South America; and the Oedaleus senegalensis (Senegalese Grasshopper) and the Zonocerus variegatus (Variegated Grasshopper) in Africa.

A grasshopper hidden in the grass.
A grasshopper hidden in the grass.

Camouflage

With many varieties being green, grasshoppers in green grass are difficult to spot by predators.

In popular culture

  • Aesop (620–560 BC), a slave and story-teller who lived in Ancient Greece, told a tale called The Ant and the Grasshopper. In this tale, the ant worked hard preparing his shelter and stores of food all summer, while the grasshopper played. When winter came, the ant was prepared, but the grasshopper has no shelter or food. He begs to enter the ant's house, but the ant refuses and the grasshopper starves.
  • "Grasshopper" is a term currently used in jest referencing a person who has much to learn. Its use originated from the television show Kung Fu (1972-1975). Caine, the young student, portrayed by Radames Pera, is receiving instruction from his Master Po (portrayed by Keye Luke) who nicknames his student "Grasshopper" as a term of endearment.
  • The Japanese superhero franchise "Kamen Rider" originally had a grasshopper motif, with a grasshopper based helmet and costume. This was later toned down in later Kamen Rider episodes, though some features of the original hero remain ("bug eyes").

See also

References

  • Firefly Encyclopedia of Insects and Spiders, edited by Christopher O'Toole, ISBN 1-55297-612-2, 2002
  1. ^ National Park Service - Insect Design - Insect Mouth Parts
  2. ^ Bizarre Foods with Andrew Zimmern aired on the Travel Channel 27 April 2008.
  3. ^ Survivorman television show, Sonoran Desert episode, broadcast on the Science Channel 1 November 2006

External links


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