6 NOTES ON MILLIPEDES. 



Sub-class Chilognatha. 

 Order Oniscomorplia. 



Short, robust Millipedes, convex above and flat below, ca- 

 pable of rolling themselves into a ball, hence popularly called 

 " Pill Millipedes." The body consists of 12 or 13 segments, of 

 which the first is very small, the second is enermously expended 

 at the sides, and the last expended laterally and posteriorly, so 

 as to entirely cover the anal region. Each typical body segment 

 consists of 7 pieces ; a large vaulted semi-circular horny plate 

 forming the upper surface, and concealing the legs, beneath this 

 on each side a small pleural plate, and between this and the two 

 legs two still smaller tracheal plates bearing the stigmata, one 

 corresponding to each leg. The legs are in contact in the middle 

 line of the body, and those of the last pair, or last two pairs, are 

 enlarged in the male and transformed into a pair of clasping 

 organs. The back plates are not furnished with scent-pores. 

 Pill-millipedes are found in North America, Europe, Africa, Asia 

 and Australasia ; some species attain a length of over 2\ inches 

 (or 60 mm.) ; they are divided into two families : — 



A. 12 segments, antennas close together. Glomeridce. 



B. 13 segments, antennae further apait. Zephroniidce. 



Pill-millipedes may possibly be confounded at first sight 

 with Woodlice, belonging to the Crustacea, and with certain 

 wingless Cockroaches, belonging to the Hexapoda, which both 

 occur in similar localities and surroundings ; the cockroach can 

 be at once detected by having only 3 pairs of legs, and the 

 woodlouse by its having only one pair of legs to each segment, 

 instead of two pairs to most segments as in the Millipedes. 

 " Moreover, the hinder end of the body in the crustacean is com- 

 posed of a number of small segments more or less closely 

 crowded together, but in the Pill-millipede the last segment is 

 much enlarged, and acts as a kind of protective cover to the 

 lower side of the body when it is spherically rolled. Of course 

 there are other differential characteristics between the two not less 

 striking than that already mentioned ; but it is needless to enter 

 into them here." Pocock, J. B. N. H. S. vol. xii, p. 269 (1899). 



