Embioptera: India
Contents |
Faunal Diversity in India: Embioptera
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
Order Embioptera constitues one of the smallest and interesting group of primitive insects. These insects show interesting combination of primitive and specialized characters. As a result, several authorities believe that these can be compared with Peripatus and Anaspids among other anthropods.
These insects are medium sized (5-2 mm), slender built, campodeiform, with chweing mouth parts and metatarsus of forelegs swollen containing glands and spinnuettes. Females are apterous, while males may be either apterous or winged; reproduction by both sexually and parthenogenetically.
These insects inhabit humid places, usually away from light. They live gregariously in the silken tunnel under bark, stone or soil block. They spin with their feet. The tunnel helps them in getting protection from the predators. Some of these insects live in association with termites, social spiders, etc.
Status Of The Taxon
Global and Indian Status
There are two hundred species and subspecies distributed over eight families in the world. In India, so far only thirtythree species have been discovered, spreding over four genera and two families. Family Embiidae contains three genera and seventeen species as follows: Pselldemibia (6 spp.) , Embia (8 spp.), Metembia (3 spp.); family Oligotomidae contains one genera, viz., Oligostoma with sixteen species.
Distribution
Thirty three species reported so far from India have been recorded from Bihar, Delhi, Goa, Kerala, Maharashtra,. Tamil Nadu, Uttar Pradesh and West Bengal. MI1RA : Ernbioplern Following is synopsis of distribution of the order in five ecosystems of India. (a) From the Himalayas : Embia major, Oligotoma gravelyi, O. montana and O. himalayensis;
O. greeniana, O. humbertina, O. josephi, O. latereillei, O. minuculav, O. saundersii and Pseudembia trundata.
Biological Diversity And Its Special Features
These insects occur in all• continents, but they are discontinuously distributed. Family Embiidae is mainly confined to India and Africa and some extended to South Europe and middle East. Family Oligotomidae is available in Asia And Australia; but the genus Haptoembia occurs in the Mediterranean and Black Sea. Family Clothidae is visible in the tropical forest of Amazon North America and Trinidad. Family Notoligotomidae occurs in Tropcal zone of Asia, Thailand and Australia. Family Embonychidae is distributed only in north Vietnam, family Aniembiidae is a new world element and family Austraembiidae is confined to East Australia. In India the species are distributed in five ecological zones and eight states as mentioned earlier.
Endemicity
This primitive group is characterised by its discontinuously distribution pattern; hence its endemicity is high. In India following fourteen out of thirty three species have been recorded as endemic. Family Embiidae : Embia major, E, minor, Pselldembia paradona, P. tnmcata., Metembia flava. Family Oligotomidae : Oligotoma anandalei, O. gravelyi, O. folias, O. c/!lJlonica indica, O. dharwariana, O. lIimalayensis, O. josephi, O. montana, O. prutllii.
Value
Studies on the members of the order Embioptera are very important both in the academic and economic point of view. Moreover, studies on their association with tremite and other arthropods may throw lights on the evolution of commensalism and socialism in insects. These insects live in. humid places with vegetation and helps in the formation of humus and improvement of the soil layers.
Threats
On going developmental work throughout the county" is resulting in reducing the habitat of this group since habitat destruction is the main threat for their survival.
Conservation And Future Studies
Habitat conseryation is to be the main effort for the conservation of this insect group. Thorough survey is to be conducted in the Himalayas, NE India, Central India and Eastern and Western Ghats for exploration and study of this insect order. There is every probablity that surveys in these areas may yield some good results including discovery of many new taxa.
Selective References
Ananthakrishnan, T. N. & Ananthasubramanian, K. S. 1956. Some Embioptera from South India. Indian J. Ellt., 17: 105-168.
Ananthasubramanian, K. S. 1956. Biology of Oligotoma Imbertiana Saussure. Indian J. Ent., 18 (3) : 226-232.
Ananthasubramanian, K. S. & Ananthakrishnan, T. N. 1960. Biology of Oligotoma minI/sCIlla Enderlein (Oligotoma : Embioptera). BI/II. Ent., 1 : 8-21. Bradoo, B. L. 1967. On the life history and bionomics of Oligotoma ceylonica Enderlein commensal in nest of the social spider Stegodyplllis sarasinonlm Karsch. J. Bombay nat. Hist. Soc., 64 (3) : 447454.
Bradoo, B. L. 1971. Two new species of Embioptera with records of others from South India. Oriental. Ins., 5 (2) : 263-267.
Bradoo, B. L. & Joseph, K. J. 1970. Life history and habits of Oligotoma greeniana Enderlein (Oligotomidae : Embioptera) commensal in nest of social spider 5tegodyplrl/s sarasinomm Karsch. Indian J. Ent., 32 (1) : 16-21.
Imms, A. D. 1913. On Embia major n. sp. from Himalayas. Trans. Linn. Soc. Zool.,. '11 : 167-195, 2 pIs. Kapur, A. P. & Kripalani, M. B. 1957. Studies in Indian Embioptera. Part 1. The Oligotimidae of India. Trans. R. Ent. Soc., London, 109 : 111-134. Mukherjee, D. 1927. On the morphology and bionomics of Embia minor sp. nov. with special reference to its spining organ. Rec. Indian MilS., 29 : 253-282, 1 pI. Ross, E. 5.1943. Two new Indian Embioptera and the Lectotype of Oligotoma borensis Hagen. Psyche, 50 : 100•108, 13 figs.
Embioptera
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Introduction
The Embioptera constitute one of the smallest and most unique order of insects. These are commonly known as embiids or web-spinners. These insects exhibit a number of unique specialisation along with certain primitive features. This led Imms (1913) to remark that these are worthy of being compared with Peripatus and Anaspids, among other Arthropods. These are medium-sized (5-25 mm), slender built, campodeiform insects, with chewing mouth parts and metatarsus of fore-legs swollen containing glands and spinnuettes. Females are apterous while males may be either apterous or winged. Reproductive both sexually and parthenogenetically.
The habit and habitat are also specialised, for the order. Embiids occur in humid places, usually shun light and are Doctural; the adults sometimes move about during the daytime if the sky is overcast. They, in all life stages, live gregariously in the silken tunnel under bark, stone or soil. They spin with their feet The threads are formed from a slaction that comes out of a few tubular bristles on their feet andhardens on contact with the air. The tunnels help in protection against predaceous insects. Oviposition and the Dumber of eggs laid under natural conditions, varies.
Besides tunnel, there are other specialized habitats. In Sudan, Embia termitophila is termitophilous and live in the colony of Bellicositermes natalensis whiie in India, some species of the genus Oligotoma, viz., O. greeniana, O. ceylonica indica and O. minuscula Uve in association with the social spider Stegodyphus sarasinorum. Generally, ants and spiders are common enemies of these insects. The Proctotrupid, Embidobia urichi is an egg-parasite and Bathylid, Mystrocnemis embiidarum larval ectoparasite.
The Embiopterans are not of much economic importance neither these are benefi~ial nor harmful to man and his agriculture, forestry etc. Even their role in food-chain is• of very minor significance. These insects are known to feed on decaying vegetable matter; thus they play the role of humification of soil. The fuller knowledge of the order may be helpful from the point of view of theories of evolution and zoogeography. The male embiopterans could also serve as an ideal demonstrating generalised anatomy of Pterygote, as pointoo out by Ross (1970). The Palaentological records of embioptcrans are fragmentry, owing presumbly due to their fragile body. The first member [Oligotoma antiqua Pictet =Hap/aembia antiqua (pictet)] appeared in the Tertiary Baltic Amber and in the shales of the Lower Permian of Kansas (Colothoda spp.), Florissant, Colo. and in' Post-tertiary of Africa and Asia. The phylogeny of embiopterans is, therefore, not definite. There does not exist unanimity in entomologists on this aspect
Tillyard (1926) opined that some of these forms belong to the order Protembiaria, which may be an offshoot of the Protorthoptera. Treading on the same line, Snodgrass (1937) basing on the male genitalia, and Kershaw (1914), basing on embryology firmly postulate that may be an Orthopteroid group. Mukherjee (1927) thought that these are only survivors of Protorthoptera
Classification
The classification of the order has its own history. The name Embioptera was coined by Shipley (1904) and it is being used consistently by Imms (1930), Metcalf and Flint (1932), Falsom and Wardle (1934), Davis (1939), and Ross (1940). Before this. certain other names were coined viz. Embidina Hagen (1885), Embidopteres Lame'ere (1900), Enlbiidina Enderlein (1903), Embiodea Kusnezow (1903), Embioidea Embiania Handlirsch (1903), Adenopoda Verhoff (1904), Oligoneura Bomer (1904) etc.
The classification of the order, presently accepted, is based on Ross (1970). The character of ODique asymmetrical male genitalia is utilised as the basis of classification of the order; in contrast, no reliable characters of taxonomic significance have been developed for females.
Ross (1970) divided the suborder Embioptera into 4 suborders viz., Embipptera and 3 suborders as "A", "B" and "e" The former is the main group, with 5 families: Clothodidae, Embiidae, Notoligotomidae, Embonychidae and Anisembiidae. SubQrder "A" of Ross included Autralembiidae: suborder "B" included a family to aCcommodate Enveja bequaertic Navas and the complex of closely related species only. known from Katanga and Northern Zambia. The last suborder, designated "e", included 2 families namely Oligo.tomidae and Teratembiidae. It is thus seen that the order is mainly comprised of 8 famili¢s having about 200 species from the whole world. Ross (1972) indicated the possibility of many more species to be added. Indian component ofthe order comprises only 33 species, so far known, under 4 genem and 2 families viz., Embiidae and Oligotomidae.
Historical Resume
A perusal of literature on the development of Embiopteran studies, reveals that it is relatively much less known than other members of "Orthopteroid" group of insects.
i) Pre-1900
During this period no Embiopteran work was contributed on the Indian material, either by Indian or foreign entomologists. However, some contributions are worth mentioning from other parts of the world. Hagen (1885) fIrst published a consolidated report on seventeen species. In the twentieth century, Krauss (1911) reported fifth species and Enderbin (1912) recorded sixty species. Davis (1940) constructed a key for identification of 140 species recorded from different parts of the world. Ross (1940, 1944) added significantly to the knowledge of the group in his "Embioptera of North America" and "A Revision" of the Embioptera or the Web spinners of the New World" Davis (1938. 44) published "Studies on Australian Embioptera" and the "Revision of Embioptera of Western Australia"
ii) 1901-1947
The first record of Indian Embioptera is available in Imms (1913) wherein he described Embia major from the Himalayas. He was followed by Mukherjee (1927) who described Embia minor from Calcutta. He also provided the biology and the bionomics of the species. Davis (1940) discovered Pseudembia paradoxa and P. truncata. Ross (1943) described Metembia [lava and Oligotoma folias and also the lectotype of O. borensis.
iii) 1948-1990
Ross (1950) in his "The Embiidae ofIndia" constructed a key for identification of genera and species known from India during that period. This included about a dozen species. Among the Indian workers Bhasin (1953) fllst reported three species from India present in the collection of the Forest Research Institute and Colleges, Debra Dun. Ananthakrishnan and Ananthasubramanian (1956) recorded some species from South India. Kapur and Kripalani (1957) worked and contributed on Indian Oligotomidae and added Olig%ma greeniana Enderlein to the fauna of India, originally described from Sri Lanka. A number of new species Oligotoma pruthii, O. anandalei, O. signata, O. gravelyi, O. montana and O. himalayensis were also added. Bradoo and Joseph (1970) reported O. greeniana from Kerala. Bradoo (1971) observed seven species of Embiids from Karnataka and Kerala coastal area, of which Oligotoma dharwariana and O. josephii Were new to science. First record of bionomics on Indian Embioptera was by Mukherjee (cf above). Ananthasubramanian (1956) reported the biology of Oligotoma humbertiana Saussure and Ananthasubramanian and Ananthakrishnan (1960) of Oligotoma minuscula Enderbin, the smallest Oligotomid, from Madras. Bmdoo (1967) studied the life-history and bionomics of Oligotoma ceylonica Enderlin and its commensalism with the social spider S tegodyphus sarasinorum Karsch. Bradoo and Joseph (1970) recorded the life history of O. greeniana and its commensalism with Stegodyphus sarasinorum.
The study on the Embiopteran fauna of different ecosystems in India is quite limited. Embia and Oligotoma and important genera occurring in India. Of these O. nigra Hagen is abundant in northern India; O. saundersii Westwood is common in the plains of West Bengal; while O. latereillei Rambur is common also the West Coast of India. Following is a synopsis of the fauna recorded from different ecosystem of India: a) Species recorded/rom the Himalayas : Embia major Imms; Oligotoma gravelyi Kapur and Kripalani; O. montana Kapur and Kripalani; O. himalayensis Kapur and Kripalani etc. b) Species recorded/rom the Gangetic alluvium~' Embia saundersii Westwood, E. minor Mukherjee, Oligotoma greeniana Enderbin etc. c) Species recordedfrom Barkuda Island, Orissa: Oligotoma anadabi Kapur and Kripalani d) Species recordedfrom Eastern Ghats: Oligotoma pruthii Kapur and Kripalani e) Species recorded/rom the West Coast 0/India: Oligotoma ceylonica ceylonica Enderlin, O. c. indica Davis, O. dharwariana Bradoo, O. greeniana Enderlin, O. humbertiana (Saussure), O. josephii Bradoo, O. latereillei Rambur, O. minuculav Endubin, O. saundarsii Westwood and Pseudembia truncata Davis.
Estimation of Taxa
In India, there are about thirty three species, spread over four genera and two families viz. Embiidae and Oligotomidae. World fauna of this group of insects is represented by 200 species in 8 families.
In Embiidae, the genus Embia Latreille occurs from Mediteranean to South Africa and India. Pseudembia Davis and Metembia Davis occur from Iraq to India. In the family Oligotomidae, the only genus Oligoloma Westwood occurs in Africa, India, Papua, etc. The following species are endemic to India:¬
a) Family: Embiidae : This family has 5 endemic species under 3 genera viz., Embia major, E. minor, Pseudembia paradoxa.P. truncata and Metembiaflava.
b) Family: Oligotomidae : This family has 9 endemic species representing only single genus Oligotoma Westwood, viz., Oligotoma annandalei, O./oUas, O. gravelyi, O. ceylonica indica, O. dharwariana, O. himalayensis, O. josephii, O. montana, and O. pruthii. Classified Treatment This insect group, as known, is a mixture of primitive and specialized features, having discontinuous distribution. The differences in opinion on the phylogeny of the group have made its taxonomy a puzzle, and the classification is dependent on males only. The classification proposed by Ross (1970) is generally accepted. The following break-up indicates the status of the order in India:
2.Oligotomidae oligotoma
The Family Embiidae Burmeister, is relatively quite well represented. This family has been considered to be a'Catch -Call' of several discrete generic groups. This is mostly confined to the Old World, with its greatest ~oncentration in India and Africa, though the genera Embia and Paraembia. range up to Southern Europe and Middle East.
The family Oligotomidae Endedein, is a well established family, including many common embiopterans. The members of this family are mainly restricted to Asia and Australia, except for the genus Haptoembia Verhoeff, which has westward extended distribution up to the Mediterranean and Black Sea. The largest genus of the family is Oligotoma Westwood, which has probably differentiated in Peninsular India. The Indian embiopterans under this genus are represented by 16 species.
The other 6 families of Embioptera which are not represented in India, may also be briefly discussed. The family Clothidae Enderlein is small, but not well defined. This includes most generalized Embioptera [Clothoda nobilis (Gerstaceker)]. Members of this family are confined to tropical forest of Amazon, North America and Trinidad. The family Notoligotomidae Ross is stated to be limited to certain Tropical Asian zone, Thailand and Australia. Embonyc hidae Navas is represented by a single known species, Embonycha interrupta Navas from northern part of North Vietnam. Anisembiidae Davis is strictly a New World family. Austraembiidae Ross embraces East Austmlian genera Australembia Ross and Metaoligotoma Davis.
The habit and habitat of embiopterans have been studied but their importance in humus fonnation has not been assessed quantitatively. Although some enemies have been discovered but detailed studies h-ave not yet been made. Therefore, it can be said that there is enough scope of studies on the ecology of the group. In India, only sporadic records of collection of the group are available. Therefore, no defmite idea could be fonned on zoogeography and fauna of the country.
Current Studies
The order Embioptera is relatively much less represented and worked out group. There is initiation in shape of listing, distribution pattern of Indian Embioptera at Z.S.1. The taxonomy and bionomics of the order has been tackled by workers at some Indian Universities and Colleges (LOyola College, Madras; D.A.V. College, Abohar and CaliGut University).
Expertise India
Elsewhere
A. P. Kapur, 8B, Circus Avenue, Calcutta 700 017. M. B. Mansukhani, 63D, Theatre Road, Calcutta 700 017. T. N. Ananthakrishnan, Entomological Research Institute, Loyola College, Madras (Tamilnadu). K. S. Ananthasubramanian, Loyola College, Madras (Tamilnadu). B. L. Bradoo, Dept. of Zoology, D.A.V. College, Abohar (Punjab). K. J. Joseph, Dept. of Zoology, University Centre, Calicut (Kerala).
Abroad
E. S. Ross, California Academy of Sciences, California (USA). R. Stefanin, Insitute de Zoologica (Italy). M. Stephen, Bioloski Institute (Yugoslavia).
Selected References
Ananthakrishnan, T. N. &Ananthasubramanian, K. S. 1956. Some Embioptera from South India; Indian 1. Ent., 17 : 105-168.
Ananthasubramanian, K. S. 1956. Biology of Oligotoma hubertiana Saussure. Indian 1. Ent., 18(3) : 226-232.
Ananthasubramanian, K. S. &Ananthakrishnan, T. N. 1960. Biology of Oligotoma minuscula Enderlein (Oliogotoma : Embioptera). •Bull. Ent., 1 : 8-21. Bradoo, B. L. 1967. On the life history and bionomics of Oligotoma ceylonica Enderlein commensal in nest of the social spider Stegodyphus sarasinorum Karsch. 1. Bombay nat. Hist. Soc., 64(3) : 447-454.
Bradoo, B. L. 1971. Two new spec ies of Embioptera with records of others from South India. Oriental. Ins., 5(2) : 263-267. Bradoo, B. L. &Joseph, K. J. 1970. Life history and habits of Oligotoma greeniana Enderlein (Oligotomidae : Embioptera) commensal in nest of social spider Stegodyphus sarasinorum Karsch. Indian 1. Ent., 32(1) : 16-21.
Imms, A. D. 1913. On Embia major n. sp. from Himalayas. Trans. Linn. Soc. Zool., 11 : 167¬195, 2 pIs.
Kapur, A. P. &Kripalani, M. B. 1957. Studies in Indian Embioptera. Part 1. The Oligotimidae of India. Trans. R. Ent. Soc., London, 109 : 111-134. Mukherjee, S. 1927. On the mo~hology and bionomics of Embia minor sp. nov. with special reference to its spining organ. Rec. Indian Mus., 29: 253-282, 1 pI.
Ross, E. S. 1943. Two new Indian Embioptera and the Lectotype of Oligotoma borensis Hagen. Psyche, 30 : 100-108, 13 figs. ~ResoUTcesoflndia:297-298: 1991
