Opiliones: India

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This is an extract from ANIMAL RESOURCES OF INDIA: Protozoa to Mammalia State of the Art. Zoological Survey of India, 1991. By Professor Mohammad Shamim Jairajpuri Director, Zoological Survey of India and his team of devoted scientists. The said book is an enlarged, updated version of The State of Art Report: Zoology Edited by Dr. T. N. Ananthakrishnan, Director, Zoological Survey of India in 1980.

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Opiliones

The members of the order Opiliones or Phalangida are the 'harvestmen', the majority of which can be recognised by their long and slender legs and segmented abdomen which is jointed to the cephalothorax across the whole breadth and not by a narrow pedicel as in spiders. The cephalothorax. is composed of six segments and is separated from the abdomen by a fairly deep groove. The carapace is generally smooth and, in most species, bears two eyes, which may be rarely absent The eyes are always situated on a prominent ocular tubercle near the middle of the cephalothorax. The body of harvestmen is usually covered with spines, pointed tubercles and bristles. On the underside of the body, the coxae of the legs almost meet in the middle, so that there is no sternum as in spiders.

The abdomen is composed of 10 segments, but these can be distinguished only in the most primitive suborder Cyphophthalmi, in others not more than 9 tergites are present The Opiliones are divided into three suborders of which the Cyphophthalmi is the most primitive and other two suborders are Mecostethi and Plagiostethi.

The adults ordinarily hide during day, but at twilight they wander out in search Qf food. Some species are often found in the fields, where they are congregate in large numbers. Sometimes, they congregate in a similar manner on the tree trunk. The name harvestmen for these creatures was probably suggested by the fact that they are most often. seen in the field during harvest time. The Harvestmen are primarily carnivorous and usually feed on fresh or recently dead animal tissues, but they also eat various organic matter such as bread, fat, the gills of fungi, etc.

The Opiliones (harvestmen) are among the most ubiquitous arachnids that are too conspicuous to escape notice, and the Indian subcontinent has a large diversity of harvestmen fauna, rich in variety as well as abundance. But unfortunately in our country practically not much research work has been done on this group. Only Roewer (1929.) made some attempts to work out the Indian harvestmen and described 167 species distributed under 40 genera of the subfamily Gargellinae of the family Phalangodidae. There are excellent works on these animals in the European countries and America Roewer's monumental work on this group "Die Weberknechte der Erde" appeared in 1923 and adopted the Simon's classification and included all harvestmen under three suborders viz., (1) Mecostethi (2) Plagiostethi (3) Cyphophthalmi, with description of about 1,600 species in 12 families.