CLASSIFICATION OF MILLIPEDES
Class Diplopoda - This class comprises fifteen orders that are distinguished by the number of legs and segments, the profile and general body form, the configuration of the head, and the position of the sperm transfer or copulatory appendages in males. The orders are combined into two subclasses based on the presence or absence of calcium in the exoskeleton and copulatory structures. The great majority of millipedes possess these features, so the orders in this subclass are further grouped into two "infraclasses."

Subclass Penicillata - body soft, exoskeleton not calcified, covered with tufts of "bristles," males without copulatory appendages, reproduction occurring without contact between sexes.

Order Polyxenida (4 families) - Occurrence: Worldwide. New World occurrence from southern Canada to Brazil, especially in warmer regions.

Figure 7. Polyxenus sp., a common millipede throughout North America. Photo by D.L. Tiemann.

Subclass Chilognatha - body hard; exoskeleton calcified; setae scattered, never in tufts; males with reproductive appendages, reproduction requiring contact between sexes.

Infraclass Pentozonia - relatively short, broad millipedes; the five segmental "sclerites" (dorsal tergite, lateral pleurites, and ventral sternite) are separate; and the last one or two pairs of legs in males are modified into clasping structures called "telopods."

Order Glomeridesmida (1 family) - flattened species with 22 segments, unable to roll into balls; similar in general configuration to the presumptive ancestral millipede. Occurrence: tropical, absent from Africa.

Figure 8. (right) General body outline of a subadult Glomeridesmus sp. Drawing by R.G. Kuhler.

Order Glomerida (3 families) - 12 segments, can roll into a perfect ball or sphere. Occurrence: Europe, Asia, North Africa and North America. North American occurrence: southern Appalachians and southeastern U.S., California to northern Central America.

Figure 9. (left) Glomeris sp. from Italy. Photo by D.L. Tiemann.

Order Sphaerotheriida (2 families) - 13 segments, can roll into a perfect ball or sphere. Occurrence: Australia, New Zealand, tropical Asia, southern Africa and Madagascar.

Figure 10. (left) Sphaerotheriids from Madagascar and Indonesia. Photo by J. Page.

Infraclass Helminthomorpha - Elongate, worm-like millipedes with varying degrees of fusion among segmental sclerites; either the anterior or both pairs of legs on segment 7, or the posterior legs on segment 7 and the anterior on segment 8, are modified into copulatory appendages or "gonopods."

Order Polyzoniida (4 families) - gonopods comprised of caudal legs on segment 7 and anterior on segment 8; body arched dorsally, tergites without "paranota" [lateral expansions]; head generally subtriangular. Occurrence: North America, Caribbean, Europe, Indian Ocean islands, eastern and southern Asia. North America occurrence: southern Quebec to southern Georgia and northwestern Arkansas; southwestern British Colombia to southern Sierra Nevada and central California coast; Vera Cruz, Mexico. One additional species has been widely introduced by commerce and now occurs in Florida and along the Gulf Coast, primarily in urban environments.

Figure 11. (right) Bdellozonium cerviculatum Cook and Loomis from the Sierra Nevada, California. Photo by D.L. Tiemann.

Order Platydesmida (2 families) - gonopods comprised of caudal legs on segment 7 and anterior on segment 8; body generally flattened, tergites with "paranota"; head generally subtriangular. Occurrence: North America, Mediterranean region of Europe, east Asia (Japan, China), southeast Asia and Indonesia. North America occurrence: southern West Virginia and central Kentucky to southern Alabama, Louisiana, and western Arkansas; Idaho; northern California; Mexico to Panama.

Figure 12. (Left) Brachycybe rosea Murray, from the Sierra Nevada, California. Photo by D.L. Tiemann.