INSECTS AND THEIR NEAR RELATIVES. 



21 



segmented ; and the abdomen bears at its end organs for 

 spinning silk (Fig. 13). 



Fig. 13. — Penceiia 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). ^'of clphaVothorax'of 

 The greater number of spiders have four dibie'f^wyma^na; 

 pairs of eyes (Fig. 17), but there may be fip;^J,^st'emum.°'^^'^ 



Fig. 15.— Tip of claw of Fig. t6.— Maxilla and Fig. 17.— Head of spider, 

 mandible of spider. palpus of male house- showing eyes and mandi- 



spider. bles. 



