CLASSIFICATION 



nerve cords, connected by transverse commissures. Integument delicate. 

 A single genus, Peripatus (Fig. 3), comprising many species. 



Diplopoda. Terrestrial. Two regions, head and body. Body 

 usually cylindrical, with numerous segments, most of which are double 

 and bear two pairs of short limbs, which are inserted near the median 

 ventral line. Eyes simple, antennae short, mouth parts consisting of a 



FIG. 3. Peripatus capcnsis. Natural size. After MOSELEY. 



pair of mandibles and a compound plate, or gnathochilarium. Genital 

 openings separate, anterior in position (on the second segment of the 

 body). Example, Spirobolus (Fig. 4). 



Chilopoda. Terrestrial. Two regions, head and body. Body long 

 and flattened, with numerous segments, each of which bears a pair of 

 long six- or seven-jointed limbs, which are not inserted near the median 

 line. Eyes simple and numerous (agglomerate in Scutigera), antennas 

 long. A pair of mandibles and two pairs 

 of maxillae. A single genital opening, on 

 the preanal segment. Example, Scolo- 

 pendra (Fig. 5). 



Insecta (Hexapoda). Primarily ter- 

 restrial. Three distinct regions head, 

 thorax and abdomen. Head with a pair 

 of compound eyes in most adults, one pair 

 of antennas and three pairs of mouth parts 

 mandibles, maxillae and labium besides 

 which a hypopharynx, or tongue, is pres- 

 ent. Thorax with a pair of legs on each 

 of its three segments and usually a pair 

 of wings on each of the posterior two seg- 

 ments; though there may be only one pair of wings (as in Diptera and 

 male Coccidae) ; the prothorax never bears wings. Abdomen typically 

 with ten segments (seldom more) and without legs, excepting in some 

 larvae (as those of Lepidoptera, Tenthredinidse and Panorpidas). Stig- 

 mata paired and segmentally arranged. A metamorphosis (direct or 

 indirect) occurs except in Thysanura and Collembola. 



FIG. 4. A diplopod, Spirobolus 

 Hiarginatus. Natural size. 



