324 



ARACHNIDA ARANKAE 



CHAP. 



with hairs, but in some genera 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, i), 

 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 



Flol80.--Spider tarsi. , Tarsus of Epeira .showing por ti OU of the subject, 

 three daws and supplemental serrate hairs (a) : . . 



2, tarsus of a Tiiomisid Spi.u-r, with tw<> daws ; The general direction 



3, 3, lateral and dorsal view of tarsus of an f n Vc.i In- rhr Iprrc rhp 



A J.A. i d i i i i UCliYt 11 I ) > 1/11C ICtio. UIlv' 



Attid Spider, showing scopula at />. J 



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. 



''''' 



