Orthoptera: India
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Faunal Diversity in India: Orthoptera
This is an extract from FAUNAL DIVERSITY IN INDIA Edited by J. R. B. Alfred A. K. Das A. K. Sanyal. ENVIS Centre, Zoological Survey of India, Calcutta. 1998 ( J. R. B. Alfred was Director, Zoological Survey of India) |
Introduction
The name of this order is derived from the greek word 'Ortho' means straight, 'Pteron' means wings. The forewings form more or less thickened tegmina, with submarginal costal vein. The order includes most common insects, viz, grasshoppers, locusts, crickets, mole crickets and grouse locusts. The most significant features of this group of insects is its jumping habit with the help of enlarged hind legs, and sound production by its auditory organs. Besides winged forms the brachypterous and apterous forms are also known in this order.
Status Of The Taxon
Global and Indian Status
This is one of the largest order of insects and also includes destructive locusts. Over 17,250 species are known to science throughout the world. More than 1,750 species, about 10% of the total world species, have been recorded from India and nearly an equal number are yet to be discovered.
Distribution
The orthopterans are distributed throughout the physiographic zones of the world but their distribution largely depends upon the vegetations like grasslands, forests and agricultural fields. Temperature, seasonal distribution of rain fall and soil conditions are some important factors which also determine the distribution of grasshoppers. India provides an unique habitat for this group of insects. There are humid grasslands in East and Northeast India, semi-arid grassplain in Northwest and Southern parts of India, vast agricultural fields, sub-mountaneous forests and scrub jungles, vegetation adjoining lakes, river basins and numerous water bodies scattered throughout the country. The members of this order range well into colder areas of the country and many species are found up to the snowclad Himalayan ranges.
The quantitative concentration of the species varies from season to season and also from one region to other regions of the country. However, in india, maximum concentration of all the species were recorded during monsoon and post monsoon season Oune to September) when the growth of all types of vegetation in the natural grassfields as well as in the agricultural fields are in optimum condition. Hazra et al. (1981,84) and Tandon et al. (1988) estimated about 200 grasshoppers (22 genera and 24 species) in a natural grassfield and 120 grasshoppers (8 genera and 10 species) in cultivated fields in West Bengal during August-September. The major species common in both natural and cultivated fields were OXtja fllscoviltata, Aiolopuos Ihalassillus tamullls, SpatllOstemum pro prnsillifentm, Acrida exaltata, Atractomorpha crmulata, etc.
On the other hand, maximum diversity of orthopteran species was encountered in the typical tropical rain forest areas of Northeastern states (Assam, Meghalaya) and Nilgiri, Wynad, Silent valley areas of South India, and the terai and dooars regions of the Himalayan foot hills. The distribution pattern of grasshoppers is changing rapidly due to the encroachment of grasslands and forests for agricultural and industrial purposes. The species which were once abundant in the grassland and forest areas and never considered as pests now occur in huge numbers in the cropfields in the form of minor pests of a potential major pest, e.g. Phlaeoba illfumata, Atractomorplla crel1l1lata and OXtja fllscovittata, the former two species were once found only in the grass fields and latter was abundant in the aquatic weeds like water hyacinth, which are now considered as major pests of paddy and vegetables in some states of India.
Biological Diversity And Its Special Features
The range of habitat diversity is exquisite in this group of insects in relation to the shape of the body. In their habits and habitats the group is so specialised that they can be grouped as follows:
Some forms live mostly on ground and are called terricoles ; many species live on flat surface of large floating leaves and are called aqllaticoles; some forms live on trees and large shrubs and are called arbicoles; some forms living mainly in dense thickets of shrubs and herbs with admixture of grasses are called herbicoles; and finally large number of forms living in grasses are called gramillicoles. The order is divided into 2 suborders, viz. , EnsHera and Califera. EnsHera has two superfamilies, viz., Tettigonoidea and Grylloidea. Califera is divided into four superfamilies, viz., Acridoidea, Tridactyloidea, Eumastacoidea and Tetrigoidea. Superfamily TeUigonoidea is divided into 4 families of which the family Tettigonidae has diversity with about 4,000 species under 21 subfamilies throughout the world. India is represented by about 80 species under 72 genera and 6 subfamilies.
Superfamily Grylloidea has twelve families, with 2,250 species distributed under 12 families and 364 genera in the world of which 181 species and 64 genera have been discovered from India. Superfamily Acridoidea has shown maximum diversity and is divided into five families of which family Acrididae and Pyrgomorphidae are widely distributed in India. Acrididae is divided into 17 subfamilies and altogether over 6,000 species under 1,000 genera are known from the world, of which 310 species under 138 genera and 14 subfamilies are known from India.
Family Pyrgomorphidae has been divided into two subfamilies. The subfamily Pyrgormorphinae includes 440 species under 148 genera from the world, of which 40 species under 19 genera are known from India.
Family Tetrigidae under superfamily Tetrigoidea has been divided into six subfamilies. A total of 988 species under 195 genera are now known from the world, of which 135 species under 36 genera are found in India. Superfamily Eumastacoidea has been divided into 7 families and 31 subfamilies. There are about 80 species occurring throughout the world, of which 28 species under 3 families and 5 subfamilies have been found in India. Superfamily Tridactyloidea is divided into 3 families and is known by 163 species from the world of which 16 species are so far known from India. A list of monotypic genera of Orthoptera in
Endemicity
There are over 200 endemic orthopteran species occurring in India. Therefore, the endemicity of the order comes round about 11% of the total species occurring in India. A beautiful taxon namely, Schizodactylus monstrosus under the family Schizodactylidae is on the verge of extinction. Only two genera under this family occur throughout the world. Out of these, only one species as mentioned above occurs in India. This is a large sand burrowing insect found along the sand beds of rivers. Due to discharge of pollutants in the river systems, its population is now sharply declining (Hazra 1983, Hazra and Tandon 1988).
Value
The representatives of this group of insects have immense scientific, ecological and economic value. Due to their population size, body size and palatability, major species of this group of insects are indispensible food of many birds and reptiles present in the grassland and forest ecosystems. Their role in the maintenance of ecological balance is beyond doubt. Therefore, they help directly in the protection of endangered species of birds and reptiles. Many species of Acridoidea are also serious pests of crops and pastures in India. They have long been recognised as crop pests probably from the time when cultivation was first practiced about 10,000 years ago. In the middle east in association with destructive locusts.
In general it is difficult to separate locusts from granshoppers specially when one talks about these group of insects in relation to crop damage. Damage by locusts, although spasmodic in both space and time, can completely or near completely destroy crops over large areas causing local famine and concomitant human physiological & psychological depression. Whereas 10% loss each year can be tolerated a 100% loss every year can mean disaster, even though the total loss over the period is no greater. It is this threat of total destruction that makes the locust the most feared of all crop pests. (Bullen, 1966).
Threats And Conservation
Human activities have chiefly affected the grasslands and scrub jungle areas of India. Much of the areas have been converted into agricultural land or huge industrial complexes. Due to the shrinkage of the grassland habitat, the population as well as diversity of species are reducing very fast. Some species are also attacking the crop fields due to lack of their natural habitat. The following are a few threatened orthopteran species as their known habitats are threatened: Peripolus pedarius, Schizodactylus mons/rosus, Gerenia bengalensis, Mesambria dllbia, Anacridillm Jlaveseens, Tagasta indica, Deltonotlls gibbiceps, Coptaera ensifera and Coptaera pllnctaria.
In recent years, the developmental activities especially in Northeastern States of India, involved more or less intensive deforestation, extended cultivation and road construction which exerted profound influence on the entire hitherto undisturbed ecosystems. The intrusion of man into the habitats of orthoptera while cultivating virgin lands, generally leads to a considerable reduction in the number of species and individuals. But, in small patches of virgin land, in depressions and in fallows grasshoppers are forced to concentrate and develop the potentiality for mass multiplication (Tandon and Khera, 1978). Therefore, measure should be taken to conserve the grassland areas for the protection of these natural foci of threatened animals.
Selected References
Bhowmik, H. K. 1986. Grasshopper fauna of West Bengal, India (orthoptera : Acri didae). Zool. Surv. India, Tech. Monograph No. 14, 1-178. Hazra, A. K., Tandon, S. K., Shishodia, M.S., Dey, A., MandaI, S. K. 1993. Insecta:
orthoptera : Acridoidea, State Funa series 3: Fauna of West Bengal, Part 4 : 287¬ 354. Kirby, W. F. 1914. The fauna of British India, including Ceylon and Burma, Orthoptera (Acrididae) : IX + 276 pp. London. Shishodia, M. S. 1987. Fauna of orissa: State Fauna Series, Tetrigidae : Orthoptera : Insecta (Grouse Locust) No.1, pI. 1 : 91-102. Tandon, S. K. 1975. On the genus Chondracris Uvarov (Insecta: Orthoptera : Acridoidea : Acrididae : Cytacanthaeridinae) in India. Dr. B. S. Chauhan Comm. Vol. 395-402.
