MILLIPEDES. 



211 



Zeplironiodesmus, occurring in Sumatra. None of the species exceed a quarter of an 

 inch in length. 



In the Helminthomorpha, or worm -like millipedes, which comprise the majority 

 of the species, the body is composed of from nineteen to over ninety segments, is 

 usually elongate and slender, and capable of being spirally coiled. The characters 

 by which this group may be distinguished from the two preceding are that the last 

 tergal plate forms a complete ring, enclosing the pair of valves and sternum, and 

 that the tracheal plates take the form of two median sternal pieces, to which the 

 legs are directly articulated. Moreover, the pleural scutes, although sometimes free, 

 are less distinct than in the preceding groups. The order is divided into the sub- 

 orders Colobognatha, Chordeumoidea, Callipodoidea, luloidea, and Polydesmoidea. 

 In the first of these the mandibles have undergone great degeneration, and in the 

 most modified forms (Siphonophora), the lower edge of the head (labrum) and the 

 lower lip (gnathochilarium) are together produced into a long, piercing snout. The 

 pedal laminae, or sterna, are always free and movable, as are rarely the pleurae. 

 The secreting pores are present on all the segments, with the exception of the first 

 four and the last ; the parts of the segments around the pores being sometimes 

 produced into wide plate- or rod-like processes covering the legs. The body 

 segments vary in number from about thirty to over seventy, although the largest 

 members of this group seldom exceed an inch in length, and are generally shorter. 

 These millipedes occur in the tropical countries of both hemispheres, one form 

 (Polyzonium germanicum) extending into Central Europe. In the Chordeumoidea 

 there are no excretory pores, but each segment bears six symmetrically-arranged 

 bristles. There are usually either thirty or thirty-two body segments ; the pedal 

 laminae are always free, and often the tergal plate is keeled, or furnished with a 

 large lateral pro- 

 cess on each side. 

 There is a pair of 

 eyes on the head, 

 and the jaws are 

 normally devel- 

 oped. 



The luloidea, 

 which is the largest 

 suborder of the 

 worm -like milli- 

 pedes, contains 

 families which may 

 be distinguished 



from the last group by having the pedal laminae united to the terga. Some of 

 the tropical species reach 6 inches or more in length, and are the largest millipedes. 

 Of the families, the Spirostreptidce are spread over all tropical countries, but 

 scarcely migrate into temperate climes ; while the Iiilidce reach their maximum 

 development in Europe and the United States, and are only sparsely represented 

 in the Tropics. The Cambalidce are remarkable for the presence of crests and 

 tubercles on their segments. 



MILLIPEDE, lulus sabulosus (enlarged twice). 



