They are very beautifully coloured including the shades of light green, brown, red or even orange coloured. They live on the grasses. Children love playing with them. They are called grasshoppers. Grasshoppers belong to the phylum Arthropoda and class Insecta. Class Insecta encompasses all the insects found all over the world. Grasshoppers are also insects belonging to the order Orthoptera. They are completely different from the crickets. The close relatives of grasshoppers are the locusts which have the capability to change their colour and prefer to pass their life cycle in the solitary as well as the migratory phases.
Features
The antennae present on the head of the grasshoppers are very short as compared to other members of Orthoptera and their ovipositors are also short. Mandibles are well developed for cutting the food. Some species are also capable of producing sound either by rubbing their hind femurs with the wings or with the abdomen and this process is termed as stridulation. If tympana are present then it is present on the sides of the first abdominal segment. The hind femora are generally very long and are used for jumping and leaping. Both hind and fore wings are present but the hind wings are membranous and the fore wings are coriaceous and are not suitable for flight. Females are generally larger than males but with short ovipositors. Males bear a single unpaired plate at the end of the abdomen while females bear two pairs of valves at the last abdominal segment which is used for digging into the soil for performing the act of egg laying. About 2,400 genera of grasshoppers are known and 11,000 species are known. The tropical wet forests also contain some species still unidentified. Grasshoppers are chiefly tropical.
Digestion and Excretion
The digestive system of grasshoppers is made up of foregut also called as the stomodaeum which includes the mouth region, the midgut also called as the mesenteron and the hind gut which comprises the anal region and also called as the proctodaeum. The mouth leads to the muscular pharynx which later on passes to the crop and the esophagus. Esophagus finally terminates into the Malpighian tubules which are the chief organs of excretion. The hindgut terminates as anus. Major portion of digestion is completed in the midgut but the digestion of some left residue completes in the hindgut. The chief composition of the excretory matter encompasses dry pellets of uric acid, urea and amino acids. The dry pellets minimize loss of excess water from the body. Digestive enzymes are secreted by the salivary glands as well as the midgut. The chief enzymes secreted by the midgut include protease, lipase, amylase and invertase. Other enzymes are also secreted by the midgut. The diet of the grasshoppers also affects the type of enzyme secreted.
Nervous System
The nervous system of the grasshoppers consists of ganglia and loose groups of nerve cells somewhat advanced as compared to that of the cnidarians. The ganglia in grasshoppers are basically present in each segment of the body but that present in the head is the largest and is considered as the brain. Neuropile is also present for the transmission of the signals from the brain. The sense organs are located on the exterior of the body in the form of tiny hairs or sensilla which consist of a sense cell and a nerve fiber and are responsible for acting towards any stimulus. Although sensilla are present all over the body but they are very much dense on the antennae, palps and the cerci. Tympanal organs are also present for reception of the sound. The sensilla are connected to the brain by the neuropile.
Reproduction
The reproductive system of the grasshoppers consists of the gonads, ducts which carry the sexual products outside the body and the accessory glands. In male grasshoppers the testes consists of a large number of follicles which are responsible for holding the spermatocytes which mature and form packets of spermatozoa. During the act of reproduction the male grasshopper introduces sperms into the ovipositor of the female by its reproductive organ termed as aedeagus and inserts its spermatophore a bundle containing sperms into the ovipositor of the female. Through the micropyles the sperm enters the eggs. After that the female lays fertilized egg pods with the help of ovipositor and the abdomen about 1-2 inches underground. The eggs can also be laid in the plant roots or even manure. Each egg pod contains tightly packed eggs which resemble the rice grains. The eggs do not hatch in the winter but as the climate becomes warmer they hatch out. In temperate zones most grasshopper pass their life cycle in the form of eggs during the cooler season and the first stage nymph hatches out when temperature rises. Youngs and the adults live only up to three months. The first nymph comes out from the tunnel underground and the rest of the nymphs follow it. As the development proceeds the grasshoppers increase in body size wings also get expansion. The development in grasshoppers is hemimetabolous or incomplete because the youngs resemble the adults.
Circulation and Respiration
The circulatory system in the grasshoppers is open and the body fluid that circulates throughout the body cavities and the appendages is the haemolymph. The dorsal vessel which is the only closed organ extends from the head through the thorax up to the hind end of the body. The dorsal blood vessel consists of two parts: the heart which is restricted to the abdomen and the aorta which extends from the heart to the head through thorax. The haemolymph is pumped in the forward direction from the hind end and sides of the body through a series of valved chambers each of which carries a pair of lateral openings called ostia. The haemolymph circulates through the aorta and is discharged through the front of the head. Accessory pumps circulate the haemolymph to the veins of the wings and to the appendages before it flows back towards abdomen. Haemolymph acts as a carrier of nutrients as well as it also carries the waste products to the Malpighian tubules to be excreted out of the body. The blood of the grasshoppers is green as the haemolymph does not transport oxygen.
Tracheae are the fine air filled tubes which open on the surfaces of thorax and abdomen through small openings called spiracles are the chief organs of respiration. The spiracles are guarded by valves which allow only exchange of oxygen and carbon dioxide. The tracheoles present at the end of tracheal tubes are the chief source of oxygen transport.
Importance
The diets of different species of grasshoppers are determined by the gut analysis. The species come under the categories of monophagous to polyphagous. In some countries grasshoppers are consumed as food as they are rich source of proteins. In Mexico they are used for filling of the snacks. Raw grasshoppers should be consumed with care as they may house tapeworms. Majority of grasshoppers are green and they show camouflage and remain well protected from their predators. Nature has provided us many alluring creatures like grasshoppers which brighten our lives in untold way.
Navodita Maurice
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