Pseudoscorpionida: India
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Pseudoscorpionida
The Order Pseudo scorpionida (or Chelonethi) are small, dorsoventrally flattened arachnida commonly called 'Pseudoscorpions' or 'false-scorpions', which resemble scorpions in the general fonn of their pedipalps and body, except that the hind part of the abdomen is not narrow as in the post-abdomen or metasQma of scorpions. They have no caudal sting. The body of pseudoscorpion is flattened, which enables these small creatures to live in narrow spaces, as beneath the bark of tree, between the leaves of a book and crevices in buildings. They are generally seclusive in habits, occurring mostly in dark, damp places, beneath the bark, in soil cover, rotten logs of wood, under stones and in poultry houses. A good number of them seem also to prefer to live in the nests of birds. Because of their natural habitat in dark places and their small size these animals escape the notice of the nabiralists. The pseudoscorpions have great diversity of form and occur in a variety of habitats. They have not, however, attracted much attention of the zoologists in our country so the number of known species is negligibly small, though they are very common and abundant. Recently, Murthy and Ananthakrishnan (1977), and Sivaraman (1980) have dealt with psedoscorption. They have attempted at a comprehensive compilation of the Indian fauna of this group including about more than 100 species distributed under 47 genera and 13 families. The psedoscorptions fauna is one of the major orders of the Arachnida and in number of species, they take the seco~d place among
Arachnida (mites not included). At present about 2,300 species, belonging to 410 genera under 19 families ofpsedoscorpions are known from the world.
The psedoscorptions are small shy creatures. The dorsal surface of the prosoma or cephalothorax is formed of a large sclerite bearing the eyes and six pairs of appendages : the -chelicerae, pedipalps and four pairs of legs. The chelicerate are complexly developed structures which serve as grasping, spinning, cleansing and sensory organs, and are pre-oral in position. Each chelicera is composed of two segments. Their fingers bear a series of complicated stnictures known as the serrulae and laminae. The serrula exterior is keel-like and set with fine teeth and attached for varying degrees of its length to the movable finger while the serrula interior, attached to the base of the fixed fmger, is even more variable in form. A flagellum, fonned of setae whose number and shape are valuable taxonomic characters, is also attached to the fixed finger.
The •mouth is situated between the basal segments of the six-segmented pedipalps. The pedipalps are enonnously developed and resemble the claws of scorpions. They serve as prehensile organs to capture and kill the prey and bear sensory hairs or setae~ The immovable finger of the chela has a row of cutting teeth along its inner edge, the last of which is considerably enlarged. Through this passes the duct of the elongated poison gland, which itself is em bedded in the finger. In certain families both fmgers are equipped with poison glands.
The four pairs of walking legs differ from those of other arachnids, in fact the tibia is unsegmented so that there is no patella. At the same time in many species, the femur is divided into two distinctly segments. The number of tarsal joints is of great systematic value and is the chief character upon which the three suborders of the psedoscorpions are differentiated. According to the basis of the segments on the legs, the order Psedoscorpionida is divided into three suborders. In the suborder Monosphyronida, each leg has six segments: coxa, trochanter, basi/emur, telofemur, tibia and tarsus. In the Diplosphyronida, the tarsus of each leg consists of the proximal metatarsus and the distal telotarsus so that the "leg appears to be made up of seven segments. The Heterosphyronida have in the fust two legs a single tarsal segment each, whereas each of the third and fourth legs has two tarsal segments. Pseudoscorpions are exclusively carnivorous and feed on living or recently killed prey such as collembolans, psocids, thysanurans and other small insects. They are not usually cannibalistic but cannibalism Ilas been observed in some Indian species like
Euryolpium indicum Murthy and Anantbakrishnan, Calocheiridius beieri (Murthy) and Oratemnus indicus (With). The poison glands seem to serve a definite purpose by secreting a toxic substance by which the prey is usually paralysed. Pseudo scorpions possess poison glands in both the fingers,_ kill their prey very quickly. The phenomenon is observed in which the chelicerae are cleaned by the chelae. Incidentally one false-scorpion has been observed by Vachon (1949) to rob another of its food after a short struggle.
Large bodied pseudoscorptions belonging to the suborders Monosphyronida and Diplosphyronida, are collected by hand picking from underneath the bark of trees and logs, underneath stone and rotten wood leaves. Medium sized specimens are collected by lifting litter and debris on a piece of white cloth. Bulk collection of the pseudoscorpions in these ways is laborious and time consuming because of their small size. The most efficient method of collecting Pseudo scorpions is the use of Berlese funnels.
An excellent scientific account of the pseudoscorpions with morphological descriptions of the species occurring in France, was published by Simon (1874-1937) and later Batzan (1891) proposed an excellent classification. The most important pioneer work on the American pseudoscorpions is that of Bank (1895) who gave a synopsis of the species known at that time and described many species from America.
After Bank, and more recently there was a monographic revisionary work of the order Chelonethi by Chamberlin (1931) who based his system on an intensive analytical study of the morphology and ecology of these creatures, and introduced the' classification which was now generally accepted by chelonethologists. Although the systematic portion of this monographical work deals with the higher categories and deals with only upto the generic level, students will find it indispensable to any serious study of the pseudoscorpions. Most of the American species are listed by Beiel (1932) in his comprehensive treatment of the world fauna. The order is a difficult one for the beginner, because of the requirements in preparation and technique which must be satisfied before any critical study can be attempted
Chamberlin has divided the order into three suborders, all ofwhich are found in India. They are based on the segmentation of the legs and may be separated as follows:
1. First and second legs with a single tarsal segment, third and fourth legs with two tarsal segments ........................................................................ Heterosphyronida (Chtltoninea)
Tarsi of all legs with an equal number of segments ....................................................... 2
2. All legs with two tarsal segments, so that the legs have six segments exclusive of the coxae; primitively four-eyed, sometimes secondarily two eyes or blind.........................................
• . • • • • . • • • • • .. • .. • ...... • • .......................................................... Diplosphyronida (Neobisiinea)
All legs with single tarsal segment; always two-eyed or blind ...........................................
.. .. .. • • . • .. • • . • • • • • . • .. •...........................................................Monosphyronida (Cheliferinea)
The Indian pseudoscorptions are represented so far by the following suborders, families and genera:
Suborder Hcterosphyronida
Family Tridenchthoniidae
Genus Compsaditha Chamberlin
Family Chthonidae
Gcnem Paraliochthonius Beier, Tyrannochlhonius Chamberlin, Lagynochthonius'
Beier, and Lechytia Balzan.
Suborder Diplosphyronida
Family Neobisiidae Suborder Monosphyronida
Family Cheiridiidae
Genera Pseudocheiridium Chamberlin and Apocheiridium Chamberlin
Family Sternophoridae
Genera Sternophorus Chamberlin and Indogaryops Sivaraman
Family Atemnidae
Genera Paratemnus Beier, Oratemnus Beier, Atemnus Canestrini, Anatemnus Beier, Micratemnus Beier, Cataiemnus Beier, Stenatemnus Beier, Tuilgrenius Chamberlin and Diplotemnus Chamberin
Family Chernetidae Genera Lamprochernes Tomosvary, Indochernes Murthy &Ananthakrishnan, Parachernes Chamberlin, Pselaphochernes Chamberlin, Ochrochernes Beier, and Orochernes Beier
Family Cheliferidae
Genera Withius Kew, Metawithius Chamberlin, Hygrochelifer Murthy &Ananthakrishnan, Ellingsenius Chamberlin, Mecrochelifer Beier, Nannocheliferoides Beier, Laphochernes Chamberlin and Lophochelifer Beier.
