Dictyoptera Blattaria: India
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The name 'Cockroach' has been derived from Spanish. Cucaracha. From the geological aspect they constitute a very Qld order, many genera and species having existed as early as the Carboniferous and Permian. This ancient group of insect is source of origin of the majority of Hemimetabolous orders, which can fold their wings at rest and is further characterised by a jugal field with many veins, and usually possessing many Malpighian tubules.
Cockroaches are placed within the Order Dictyoptera. Dictyoptera means dictyon, a network; pteron, a wing. Most cockroaches are moderately large insects, even though some species measure only 5 mm in length. The body is strongly depressed and the abdomen bears two caudal appendages. Besides this, males have two further appendages. They are brown or brownish -black in general colour. The head is bent 'downward and covered by a shield -like pronotum. The mouthparts are fonned for chewing. The antennae are long and many -jointed. They are usually four winged, though some species may be wingless.
They are more fully developed in the males; in the females they may be reduced or absent The two pairs of wings differ in size and structure. The fore-wings are generally stronger, tough and elytra-like, the hind wings broad and membranous. They are not used much for tlight, however, for cockroaches fly only short distances, the chief organs of locomotion .being the legs which have greatly developed coxae and five-jointed tarsi.. The metamorphosis is incomplete. The eggs are enclosed in characteristic purse-like Oothecae which the females carry at the end of the abdomen often for severa} days until they find a place to conceal the capsule.
The members of this group have economic and medical importance. This topic falls under three beadings (1) Consumption of human food stuffs or crops, (2) Vectors of disease or parasitic organisms of man or domestic animals, (3) Spoilation of food and nuisance value in houses and buildings as a troublesome pest. There are a number of records of cockroaches causing damage to plants by eating roots or flowers of the plants. Cockroaches feed upon the bark oftrees or fruits. P. surinamensis (L) is the most often cited species causing massive destruction of tobacco plants, according to Roeser (1940). The importance of cockroaches as vectors of vertebrate pathogens is well known.
The higher classification of the Order poses certain difficulties according to Rehn (1951). The modern classification centre round the work of Chopard (1938), Princis (1962-65), Rehn (1951) and Mckittrick (1964), whose main interest were directed towards living forms. Princis (1951¬1971) reviewed many aspects of cockroach taxonomy. According to Mckittrick, Rehn and Princis have developed separate classifications solely on the ground of skeletal characters of different groups and therefore he attempted to employ skeletal, myological and behavioural inform~tions on the elucidation of systematic relationships. Roth's contribution is mainly based on applied work in this group. Princis divided Indian Blattids into 14 families and 8 subfamilies.
Earlier workers like Saussure (1863-1896), Brunner (1865-1893), Walker (1868, 1871), Kirby (1903, 1904), Chopard (1921, 1924) and in recent years, •Rehn (1903, 1951), Bey-Bienko (1938, 1950, 1957, 1965,1969), Mckittrick (1964-1965), Asahina (1955,1964), Princis (1951,1971) and Roth (1952, 1986) have described a number of species. As a result of above studies a total of about 4,200 species are recorded from all over the world, out of these 156 species are found in India.
Studies from Different Environs
Cockroaches thrive best in tropical and subtropical climates and are introduced throughout the world through transportation of commercial products. District-wise distribution of Indian species is not yet fully known, except for Orissa and West Bengal.
Blattids are known to occur in almost all the major ecosystems in India. Although general faunistic surveys have been made by scientists of Z.S.I. from various parts of the country, still further more explorations are needed for obtaining comprehensive knowledge on the group. Recently the Zoological Survey of India has undertaken the project of preparing 'State Fauna' of different States of India and the Blattid Fauna of Orissa and West Bengal are outcome of such studies.
K.P. Mukherjee, Z.S.I., 'M' Block, New Alipore, Calcutta-700053.
L.M. Roth, Pioneering Research Division, U.S. Army Natick Laboratories, Natick, Massachu. 01760 (U.S.A). Syaziro Asahina, National Institute of Health, Tokyo (Japan).
Kirby, W.F. 1904. Syn. Cat. brth. London, 1 : 61-205.
Princes, K. 1951-1971. Orthopterorum Catalogue, Part 3 : 1-74; Part 4 : 75-172; Part 6 : 173¬281; Part 7 : 282-400; Part 8 : 401-614; Part 11 : 615-710; Part 13 : 711-1040; Part 14 : 1041-1224.
Rehn, J.W.H. 1951. Classification of the Blattaria as indicated by their wings. Mem. Amer. Ent. Soc., No. 14 : 1-134, 12 pIs.