4o8 ZOOLOGY 



A pair of poison glands are found in the thorax, closely 

 applied to the walls of the stomach. The ducts are coiled, and 

 open near the bases of the chelicerae ; muscle fibres are described 

 near the orifice, and the contraction of these is believed to eject 

 the poison into the wounds caused by the chelicerae. 



Two simple eyes occur in the head. The animals are 

 nocturnal, and spend the day under stones or rubbish, or in 

 holes in the ground. They are extremely voracious, and live 

 on large insects, such as beetles and grasshoppers ; they will 

 even attack scorpions, and small vertebrates such as lizards 

 and mice. The female lays about fifty eggs at a time, and the 

 young are hatched in an immature condition. 



Class V. Araneida (Spiders). 



Characteristics. — Abdomen wnsegmented, soft, and stalked; 



chelicerae with poison glands, pedipalpi leg-like, two or four 



lung sacs, and four or six spinnerets. 



Epeira diademata is one of the largest species of British 

 spider, and at the same time is a very common one, being 

 found in its wheel-shaped web in most gardens and woods ; it 

 therefore serves as a convenient type of the order. 



The head is united with the thorax, but the abdomen is 

 constricted at its base, and being swollen and unsegmented, 

 gives a very characteristic appearance to the members of this 

 group. 



Appendages of Epeira. 



1. Chelicerae. 4. 2nd pair of walking-legs. 



2. Pedipalpi. 5. 3rd „ 



3. 1st pair of walking-legs. 6. 4tli ,, ,, 



The chelicerae are two -jointed, the terminal joint being 

 curved and pointed, and capable of folding down in a sub- 

 chelate fashion; at the base of these appendages lie a pair of 

 poison glands, and these pour their secretion through a duct 

 which opens to the exterior near the tip of the terminal joint. 

 This poison is capable of killing insects and seriously affecting 

 larger animals. 



The pedipalpi have a cutting blade-like basal joint which 

 takes part in mastication, as is the case in Limulus, Scorpio, 



