294 PERIPATUS, MYRIOPODS, AND INSECTS. 



External Characters. 



The Head. 



is vertically 

 elongated and 

 separated from 

 the thorax by a 

 neck. 



The Thorax. 

 It consists of three 



segments : — 

 {a) prothorax, 

 (.5) mesothorax, 



{c) metathorax. 

 (Each segment i; 



bounded by 2 



dorsal tergum. 



and ventral 



sternum.) 



The Abdomen. 



It consists of 10 (or 



ii)distinct seg- 

 ments, with 

 terga and ster- 

 na as in the 

 thorax. 



Appendages of the Head. 



:. A pair of stout toothed mand- 

 ibles working sideways. 

 ;. The first maxillae, each con- 

 sisting {a) of a basal piece or 

 protopodite with two joints — 

 a basal cardo, a distal stipes ; 

 {k) of a double endopodite 

 borne by the basal piece, 

 and consisting of an inner 

 lacinia and a softer outer 



falea ; 

 an exopodite or maxillary 

 palp also borne by the basal 

 piece, and consisting of five 

 joints. 

 ^. The second pair of maxillae, 

 fused together as the "labi- 

 um,'' consisting {a) of a fused 

 basal piece or protopodite 

 with two joints — a basal sub- 

 mentum, a smaller distal 

 mentum ; on each side this 

 protopodite bears 

 ((^) a double endopodite (ligula) 

 consisting of an inner 

 lacinia, and an outer para- 

 glossa ; 

 (c) an exopodite or labial palp, 

 consisting of three joints. 



The Appendages of the 

 Thorax. 



(a) First pair of legs. 

 (3) Second pair of legs. 



(tr) Third pair of legs. Each leg 

 consists of many joints — a 

 basal " coxa " with a small 

 "trochanter" at its distal 

 end, a " femur," a " tibia," 

 a six-jointed tarsus or foot 

 ending in a pair of claws. 



Appendages (?) of the 

 Abdomen. 



Two cigar-shaped tactile ana] 

 cerci, attached under the 

 edges of the last tergum, 

 are possibly relics of the 

 last abdominal appendages. 



The ninth sternum of the male 

 bears a pair of styles, pos- 

 sibly relics of appendages. 



Both sexes have complex hard 

 structures (gonapophyses) 

 beside the genital apertures. 

 They are possibly relics of 

 appendages. 



Other Structures on the 

 Head. 



The antennae (probably not 

 homologous with append- 

 ages), long, slender, many 

 jointed, tactile. 



The large black compound 

 eyes. 



The "upper lip" or labrum, 

 in front of the mouth. 



The white oval patches near 

 the bases of tne antennee, 

 possibly sensory. 



Other Structures on the 

 Thorax. 



(^) A pair of elytra or wing- 

 covers (modified wings) 



rudimentary in female of 

 P. orientalis. 



id) A pair of membranous 

 wings, sometimes used in 

 flight, folded when not in 

 use, absent in female of 

 P. OTieniaJis. 



Between the segments of the 

 thorax are two pairs of 

 respirator^' apertures or 

 stigmata. 



Other Structures on the 

 Abdomen. 



A pair of stigmata occur be- 

 tween the edges of the 

 terga and sterna in the 

 first eight abdominal seg- 

 ments. There are there- 

 fore twenty stigmata in all. 



The anus is terminal, beneath 

 the tenth tergum of the 

 abdomen ; a pair of "podi- 

 cal plates" lie beside it. 



The genital aperture is ter- 

 minal, ventral to the anus. 



The opening of the sper- 

 mntheca — the female's 

 receptacle for sperma- 

 tozoa — lies on the ninih 

 sternum of the abdomen 



