ARACHNIDA 



105 



Appendages. There are two pairs of mouth-parts. The 

 mandibles or chelicerae are strong and composed of two por- 

 tions, the basal falx and the sharp-pointed fang, in which is a 

 small opening, the outlet of the poison gland. The palpi are 



Fig. 78. The bird-spider (Myg'ale avicular'ia) capturing a humming-bird. 

 (From Holder's " Zoology," American Book Co., Publishers.) 



long and limb-like and are often mistaken for a fifth pair of 

 thoracic legs. The basal joints are broad and adapted for 

 chewing the food. They are called the maxillae. Then follow 

 four pairs of seven-segmented legs used for locomotion. The 

 spinnerets on the abdomen are homologous to paired appendages. 



