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 the short-horned grasshopper. Species that change colour and behaviour at high population densities are called locusts.
Grasshoppers have antennae that are generally shorter than their body and short ovipositors. They also have pinchers or mandibles that cut and tear off food. 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 (crickets), 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).
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.
Grasshoppers prefer to eat grasses, leaves and cereal crops. Some will tend to eat from a single host plant, while others will eat from a variety of sources throughout the day. Only one of the 8000 species of grasshopper will only eat a single species of plant.
The digestive system of insects includes a foregut (stomodaeum, the mouth region), a midgut (mesenteron), and a hindgut (proctodaeum, the anal region). The mouth is distinct due to the presence of a mandible and salivary glands. The mandible can chew food very slightly and start mechanical digestion. Salivary glands digest the food chemically, though only carbohydrates in the grasses and such they eat. The mouth leads to the muscular pharynx, and through the esophagus to the crop. The crop has the ability to hold food. From the crop, food enters the gizzard, which has teeth like features in it. From there, food enters the stomach. In the stomach, digestive enzymes mix with the food to break it down. These enzymes originate from the gastric caeca surrounding the stomach. 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.
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.
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.
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 greenRespiration 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.)
In certain countries, grasshoppers are eaten as a good source of protein. In Mexico for example, chapulines are regarded for their high content of protein, minerals and vitamins. They are usually collected at dusk, using lamps or electric lighting, in sweep nets. Sometimes they are placed in water for 24 hours, after which they can be boiled or eaten raw, sun-dried, fried, flavoured with spices, such as garlic, onions, chile, drenched in lime, and used in soup or as a filling for various dishes. They are abundant in Mexican food and street markets, particularly in the central regions.
They are served on skewers in some Chinese food markets, like the Donghuamen Night Market.
Raw grasshoppers should be eaten with caution, as they may contain tapeworms.
In some countries in Africa, grasshoppers are an important food source, as are other insects, adding proteins and fats to the daily diet, especially in times of food crisis. They are often 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.
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.