464 MYRIAPODA 



adapted for biting, except in the Polyzoniidae, in which the mouth parts 

 are suctorial. The Chilopoda, like the insects, have two pairs of maxillae; 

 the other Myriapoda have but one pair. In the Chilopoda, also, the first 

 pair of legs project forward beneath the head and are transformed into 

 hook-like claws or maxillipeds, each of which has a poison gland. Myria- 

 pods possess a pair of eyes, each consisting of a group of ocelli; in 

 Scutigera, however, compound eyes are present. The internal organs are 

 similar to those of insects. The sexes are separate, the single genital pore 

 in the Chilopoda being in the penultimate segment and the paired pores 

 of the Diplopoda in the second body segment. All Myriapoda lay eggs. 

 The young are born as larvae with three pairs of legs in the Pauropoda 

 and Diplopoda and six, seven, or more pairs in the Symphyla and Chilo- 

 poda; in certain of the latter group the larva possesses las many legs as 

 the adult, although they are not all well grown. 



All Myriapoda are terrestrial animals which live in dark, damp places 

 and avoid the light. The Chilopoda live on animal and most of the 

 Diplopoda on vegetable food. 



History. Myriapods have been known from time immemorial and 

 usually much feared on account of the dangerous bite of certain of them. 

 Aristotle mentions both centipeds and millipeds, using the still familiar 

 names of Scolopendra and Julus. Both of these names were adopted by 

 Linna3us for his two genera of the 'animals, which he placed among the 

 Insecta aptera. The name Myriapoda was created by Latreille in 1796. 

 The animals were, however, retained among the insects until 1814, when 

 Leach formed a separate class of them equivalent to the Insecta. The 

 career of the group since that time has been a checkered one, having been 

 placed by some authors among the Crustacea and by others among the 

 Arachnida or the Insecta. Its right to be considered an independent 

 group may be said to have been definitely fixed by Newport (1844) and 

 Koch (1847). In later years attention has been called to the fact by 

 Kingsley,* Verhoeff, and others that the Myriapoda form two groups 

 instead of a single one, one of which, the Chilopoda (Latreille 1817), stands 

 in close relationship to the insects, "while the other, the Progoneata 

 (Pocock 1895), occupies an independent position. 



The number of known species of Myriapoda is about 1,000, grouped 

 in two orders. 



Key to the orders of Myriapoda: 

 a t Genital pore near forward end ; body usually cylindrical, with mostly 



2 pairs of legs to a segment 1. PROGONEATA 



o, Genital pore near hinder end ; body flattened, with 1 pair of legs to a 



segment 2. CHILOPODA 



* See "The Classification of the Arthropoda," by J. S. Kingsley, Am. Nat., Vol. 28. 

 pp. 118 and 220, 1894. 



