324 



ARACHNIDA ARANEAE 



with hairs, but iii some genei'a the clothing is so sparse that 

 they appear glossy, while in others they have a positively shaggy 

 appearance. Stouter hairs or " bristles " are often present, and 

 some of the joints are also often furnished with " spines," which 

 in many cases are erectile. 



The tarsi of all spiders are furnished with terminal claws, 

 usually three in number, though in some families (Drassidae, 

 Thomisidae, etc.) there are only two. The two principal claws 

 are paired and usually dentated, though the number of their 

 teeth may be unequal. The third claw, when present, is always 

 smaller, median, and inferior. 



In many spiders of climbing habits the place of the third 

 claw is taken by a remarkable tuft of club-like hairs termed a 



"scopula" (Fig. 180, 5), 

 by means of which they 

 are able to cling to 

 smooth surfaces where 

 claws would be able to 

 obtain no hold. In some 

 species there is a special 

 false articulation — the 

 " onychium " — at the 

 end of the tarsus to 

 bear the claws. 



In the Cribellatae the 

 metatarsus is always fur- 

 nished with a comb-like 

 organ, the "calamistrum," 

 correlated with an extra 

 spinning apparatus, the 

 " cribellum," but this 

 will be dealt with when 

 we reach the systematic 

 portion of the subject. 



The general direction 

 taken by the legs, the 

 comparative length of 

 the different joints, their armature of hairs, bristles, and spines, 

 and the number and conformation of the tarsal claws, are points 

 of great importance in the classification of Spiders. 



Flo, 



■Spider tarsi. 1, Tarsus of Epeira Aiov/mg 

 three claws and supplemental serrate hairs {a) ; 



2, tarsus of a Thomisid Spider, with two claws ; 



3, 3a, lateral and dorsal view of tarsus of an 

 Attid Spider, showing scopula at b. 



