INSECTS AND THEIR NEAR RELA TIVES. 
21 
segmented ; and the abdomen bears at its end organs for 
spinning silk (Fig. 13). 
Fig. 13 .—Pencetia viridans. (From the Author’s Report on Cotton Insects.) 
The mandibles (Fig. 14, md) consist of two segments, 
a strong basal one and a claw-shaped terminal one, at 
the tip of which a poison gland opens (Fig. 
15). It is by means of these organs that 
spiders kill their prey. The palpi are leg¬ 
like in form, but differ greatly according 
to sex. In the female the last segment of 
the palpus resembles a foot of the spider, 
and is usually armed with a well-developed 
curved claw. But in the male the corre¬ 
sponding segment is more or less enlarged, 
and very complicated in structure (Fig. 16). 
The greater number of spiders have four 
pairs of eyes (Fig. 17), but there may be 
Fig. 14.—Lower side 
of cephalothorax of 
a spider; md, man¬ 
dible; mx y maxilla; 
A palpus; /, lower 
lip; 
Sy sternum. 
Fig. 15.—Tip of claw of 
mandible of spider. 
Fig. t 6.—Maxilla and 
palpus of male house- 
spider. 
Fig. 17.—Head of epider, 
showing eyes and mandi¬ 
bles. 
