288 TEXTBOOK OF ZOOLOGY 



does not form a direct link between the other tracheate arthropods 

 and the annelid stock, but is best regarded as an offshoot from the 

 base of the arthropodan stem." 



Very little is known about the habits of the onychophores, except 

 that they live under stones and the bark of trees, feeding upon small 

 insects and spiders which they capture in a slime produced and 

 forcefully discharged from glands which open on the oral papillae. 

 Many of the species are viviparous, a single female producing as many 

 as thirty living young in a season. 



About seventy-three species and fifteen genera are known from the 

 two families Peripatopsidae and Peripatidae. A number of species 

 in the family Peripatidae are found in tropical America; Macro- 

 peripatus perrieri (Bouvier) is found at Vera Cruz, Mexico; while 

 the species of the family Peripatopsidae are confined to New Guinea, 

 Australia, Tasmania, New Zealand, Cape Colony, and Chile. 



The classes Diplopoda and Chilopoda are considered by some au- 

 thors as orders of the class Myriapoda. The more recent students 

 of these groups, however, have adopted the plan of classification fol- 

 lowed here. 



Fig-. 163. — Peripatus capensis. Natural size. (After Moseley from Folsom's 

 Entomology. Redrawn by Nelson A. Snow.) 



Myriapoda 



The Diplopoda are terrestrial arthropods commonly called mille- 

 pedes. The body is composed of three regions: the head, thorax or 

 trunk, and the ahdomen. The head bears a pair of short antennae, 

 ocelli, and mouth parts consisting of a pair of mandiUes and a pair 

 of maxillae. Just back of the head is a segment with a well-developed 

 tergite, the collum, considered by some students of this group as a seg- 

 ment which has played an important role in the formation of the head 

 in some of the other groups of arthropods. A single pair of legs seem, 

 however, to belong to this first segment, as does a single pair of legs 

 to the three following segments. These four segments are said to 

 constitute the thorax. Ducts from the reproductive organs open at 

 the base of the second pair of legs on tlie third body segment. 



The abdomen consists of an indefinite number of segments, each 

 consisting of a tergum and two sterna. Each sternum bears two pairs 



