270 



COLLEGE ZOOLOGY 



Anterior view of head 



Eyes 



Poison gland 



Chelicero 



Duct 



Chelicera 



Tip of leg 

 with claws 



Anterior view showing 

 poison glands 



Accessory spinning 

 organ 



Spinnerets 



Anus 



Cocoon of garden 

 spider 



Ventral view of posterror end 

 of abdomen with spinnerets 



Figure 163. Structural details of spiders and a cocoon. 



162). Just back of the tracheal opening are 

 three pairs of tubercles or spinnerets (Figs. 

 162 and 163) used for spinning threads. The 

 anus lies posterior to the spinnerets. 



Internal anatomy 

 and physiology 



The spider feeds mainly on insects; and 

 because it can ingest only liquid food, the 

 solid parts are liquefied by the action of 

 powerful digestive enzymes contained in a 

 fluid which is regurgitated into or over its 

 prey. Actually, spiders ingest food in two 



ways: (1) those with weak jaws puncture 

 the body of the insect with their fangs, and 

 then alternate between injecting digestive 

 fluid through this hole, and sucking back the 

 liquefied tissues, until only an exoskeleton 

 remains; (2) those with strong jaws crush 

 the insect into small pieces between their 

 jaws as the digestive enzymes are regurgi- 

 tated over them. Only a small mass of indi- 

 gestible material, such as the sclerotized 

 parts, remains to be discarded. In feeding, 

 suction is produced mainly by the enlarge- 

 ment of the sucking stomach. 

 The digestive system is made up of a 



