388 CHARACTERS OF INVERTEBRATE ANIMALS 



beings, but extend also to domestic animals, such as sheep, and 

 camels. This creature resembles a large spider in appearance: 

 its body is about 2 inches long and its legs long and hairy. 

 There are great differences of structure and proportion as com- 

 pared with a Scorpion. The body is unique among Arachnids 

 in being distinctly divided into head, thorax, and abdomen, much 

 as in an insect, and the last region is composed of ten segments 

 and cylindrical in shape, there being no sting-provided tail. A 



further resemblance to insects is 

 found in the breathing organs, 

 which consist of air-tubes, opening 

 to the exterior by three pairs of 

 stigmata situated on the under 

 surface, the first at the bases of 

 the second legs, and the others on 

 F;g..3s.-commonM^c^spider(G«&.rf.. ^^ abdomen. As in a Scorpion, 



the first appendages are nippers, 

 here of very large size, and constituting the chief offensive 

 weapons, since poison glands open upon them. The pedipalps, 

 however, are not, as in a Scorpion, stout and pincer-bearing, 

 but slender leg-shaped structures having a forward direction and 

 acting as tactile organs. The first pair of legs closely resemble 

 the pedipalps in appearance and function, and it may be noted 

 that these four similar appendages are provided at their bases 

 with cutting projections, situated at the sides of the mouth and 

 serving as jaws. The remaining legs are attached to the thorax, 

 as in an insect, the resemblance being emphasized by the fact 

 that each ends in a claw-bearing tarsus. There is nothing to 

 correspond to either the operculum or the combs of a Scorpion, 

 and only two simple eyes are present, placed on the front of the 

 head close to the middle line. 



Order 3. — FALSE SCORPIONS (Pseudoscorpionidje) 



False Scorpions are minute widely - distributed animals not 

 unlike Scorpions in appearance, the resemblance being due to 

 similarity in the appearance and structure of the chelicerae, pedi- 

 palps, and walking-legs. There are, however, no poison-glands, 

 and the broad flat abdomen does not narrow into a tail. Breathing 

 is effected by means of air-tubes, which open on the under side 



