Subphylum Myriapoda

Myriapoda ("many feet") is a subphylum of elongate arthropods with bodies divided into a head and trunk with numerous segments, most of which have uniramous appendages; no pronounced tagmatization is evident. Myriapods range in length from 0.5 to 300 mm and are primarily terrestrial. Most live in humid environments, commonly in caves. Some have invaded arid habitats, but few are aquatic. Four classes are recognized: Diplopoda (millipedes), Chilopoda (centipedes), Pauropoda, and Symphyla, with 10,000, 3000, 500, and 160 species, respectively. The last two are minute dwellers of the forest floor that consume living or decaying vegetation. Symphylans look somewhat like centipedes but the adults have 14 trunk segments and 12 pairs of limbs; the posterior end of the trunk has two conical cerci and spinning glands. Members of the class Pauropoda are soft-bodied, blind myriapods with 9 to 11 leg-bearing trunk segments and branched antennae.

FIGURE 4 Members of the subphylum Myriapoda. (A) Centipede (class Chilopoda). (Photograph by Jim Kalisch, courtesy of University of Nebraska Department of Entomology.) (B) Millipede (class Diplopoda), coiled in a defensive posture. (Photograph by D. R. Parks.)

Hexapods have three major body regions (head, thorax, abdomen) and six thoracic legs.

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