a 2A: ARACHNIDA—ARANEAE CHAP. 
with hairs, but in some genera the clothing is so sparse that 
they appear glossy, while in others they have a positively shagey 
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 deutated, 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-hke 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 
Frc. 180.—Spider tarsi. 1, Tarsus of Lpeira showing portion of the subject. 
three claws and supplemental serrate hairs (@) ; i 
2, tarsus of a Thomisid Spider, with two claws ; The general direction 
3, 3a, lateral and dorsal view of tarsus of an 4,1], by , 
: by the legs, the 
Attid Spider, showing scopula at 0. taken ) ae be 
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. 
