B. SUB-CA,ASS CHILOGNATHA. Integument strengthened by deposition of salts of lime. Hairs, when present, occur singly, not in tufts. Sexually modified limbs in the male on the 7th seg ment or at the hind end of the body.
I. Opisth.andria. Male has sex ually modified limbs (one or two pairs) at the hinder end of the body.
Order Limacomorpha. Body with 22 segments. Body can not roll into a ball. Example: Glomeridesmus (fig. 2).
Order Oniscomorpha. Body with 14-16 segments. Body will roll into a ball. Example: Glomeris (fig. 3). 2. Proterandria. Sexually modified limbs on the 7th segment in the male.
Superorder Eugnatha. Not more than seven pairs of walk ing legs in front of the sexually modified limbs of the 7th seg ment.
Order Polydesmoidea. 19 to 22 body segments. The first pair of limbs of the 7th segment modi fied in the male, the second pair is a normal pair of walking legs. Examples: Polydesmus, Platyrhacus (fig. 4).
Order Nemato-pliora. 26 or more body segments. One or both pairs of limbs of the 7th segment modified in the male. Silk glands present. Example: Brachychaeteuma.
Order Juliformia. More than 4o cylin drical body segments. No walking legs on the 7th segment of male. No silk glands. Examples : lulus, Blaniulus, Spirostreptus (fig. 6).
Superorder Colobognatha. 8 pairs of walking legs in front of the sexu ally modified legs of the male. Ex ample : Poly ,opium (Head in fig. 7). Structure.—The head bears one pair of antennae and the masticatory apparatus which consists of a pair of mandibles and a pair of fused appendages modified to form a single plate-like structure, the gnathochilarium.
In most millipedes paired simple eyes (ocelli) occur singly or grouped, but some are blind. Most millipedes are pro vided at the sides of the head with a sense-organ (organ of Tomosvary) of unknown function.
In the Pselaphognatha the integument remains soft but in other millipedes the cuticle is strengthened by the deposition of lime salts within its substance except in places where flexibility is necessary for movement. The
roof and side-walls of the typical trunk segment are fused together to form a single pleurotergite almost encircling the body, the floor being formed by two small plates, the sternites, placed one in front of the other. Associated with each sternite is a pair of walking legs. More fusion, or less, accounts for differences in this arrangement in different millipedes. In many there is in addition one pair of protective "stink glands" opening on each pleuroter gite. The digestive tube, heart, main nerve cord and breathing apparatus (tracheae) are in general like those of the centipede (q.v.). The reproductive system lies below the gut and opens in the third body segment.
The origin of the double segment in dipiopods is obscure but an additional pair of masticatory appendages just behind the mandi bles has been found in the embryo of Spirostreptus. The young are hatched from the egg with three pairs of walking-legs.
BIBLIocRApiry.—The literature in English and French is very scat tered. The best modern accounts are in German: Carl Attems, "Diplo poda" in Handbuch der Zoologie, vol. iv. (1926) ; K. W Verhoeff, "Diplopoda," which includes an account of fossil forms, in Bronn's Klassen and Ordnungen des Tier Reichs, vol. V. (Leipzig, 5926-27) ; K. W. Verhoeff, Die Diplopoden Deutschlands (Leipzig 1910-14). On economic status, see S. G. Brade Birks, Supplement to Lancashire and Cheshire Naturalist (Dec. 1923).
See also CENTIPEDE ; MYR1APODA ; PAUROPODA ; SYMPHYLA.