DIPLOPODA. 



591 



o/n 



trunk segments, the fifth segment 

 bears two pairs of rudimentary 

 legs beneath the integument, and 

 the sixth has one pair. In Julus 

 the just-hatched larva is very similar 

 to that of Polydesmus. In the 

 species in which the number of seg- 

 ments in the adult is constant, 

 sexual maturity with development 

 of the copulatory limbs is attained 

 after the formation of the full num- 

 ber of segments. In forms in 

 which the number of segments is 

 inconstant it would appear that 

 formation of new segments must 

 take place after attainment of 

 sexual maturity. 



The Diplopods are sluggish 



animals and live mainly on 



vegetable substances ; some 



devour animal excrements, and 



a few are, occasionally at least, 



carnivorous. They avoid the 



light and live in damp places FIG . 353 ._ Newly hatched larvaof Polydesm ^ 



under stones, etc. They are 



useful in nature in helping to 



destroy decomposing organic 



matter, and some species (e.g. of Julus} are known as wire- 

 worms. They are found all over the world, 

 but the largest and most striking species are 

 tropical. 



Sub-order 1. Pselaphognatha.* 



Small Diplopods with soft chitin without calcare- 

 ous deposit, with 10-12 body segments carrying 13 

 pairs of legs, with toothed hairs in tufts on the 

 pleura and in transverse rows on the terga (Fig. 354), 

 without foramina repugnatoria (glandulae odoriferae). 

 The labrum is free ; the mandibles are buried in 

 the mouth-cavity and rub against the roof of the 

 mouth which is armed with teeth ; the maxillae are 

 reduced, consisting of little more than a pair of 

 palps attached to a basal plate. The male is without 

 the copulatory appendages, and the anus is in the 

 penultimate segment. The coxae of the legs are 

 FIG. 3J .Polyxenus widely separated from one another and there is a well- 

 LatzelK developed sternal region. Europe, Asia, America. 



lbr 



* Latzel, op. cit., 2, p. 69. F. G. Sinclair, Q.J.M.S., 30, 1889, p. 87. 



