HOW ANIMALS EAT. 53 



The Arthropoda exhibit a great variety of means for 

 procuring nourishment, in addition to the suctorial con- 

 trivances already mentioned, the innumerable modifica- 

 tions of the mouth corresponding to the diversity of food. 

 Millepedes, Caterpillars, and Grubs have a pair of horny 

 jaws moving horizontally. The Centipede has a second 

 pair of jaws, which are really modified feet, terminated 

 by curved fangs containing a poison-duct. The Horse- 

 shoe Crab uses its feet for prehension, and the thighs, or 

 basal joints, of its legs to masticate the food and force it 

 into the stomach. The first six pair of legs in the Lob- 

 ster and Crab are likewise appropriated to conveying food 

 into the mouth, the sixth being enormously developed, 

 and furnished with powerful 

 pincers. Scorpions have a 

 similar pair of claws for pre- 

 hension, and also a pair of 

 small forceps for holding 

 the food in contact with the 



mOUth. In their relatives, FIG. IS. One of the Fangs, or Perforated 



the Spiders, the claws are Mandible,, of the spider, 



wanting, and the forceps end in a fang, or hook, which is 

 perforated to convey venom. 20 



\,The biting Insects, as Beetles and Locusts, 'have two 

 pairs of horny jaws, which open sidewise, one above and 

 the other below the oral orifice. The upper pair are called 

 mandibles; the lower, maxillae. The former are armed 

 with sharp teeth, or with cutting edges, and sometimes 

 are fitted, like the molars of quadrupeds, to grind the 

 food. The maxillae are usually composed of several parts, 

 some of which serve to hold the food, or to help in divid- 

 ing it, while others (palpi) are sensory. There is generally 

 present a third pair of jaws the labium which are 

 united in the middle line, and serve as a lower lip. They 

 also bear palpi. The Mantis seizes its prey with its long 



