82 Key to Families of North American Insects. 



the second to the seventh segments are provided with ventral 

 styles; apex of abdomen without median process, but with paired 

 cerci; mouthparts partly concealed within the head, but the 

 palpi extended; tarsi one-jointed; no metamorphosis. 



ORDER RHABDURA. 



Very thinly chitinized, small, slender, terrestrial insects with 

 somewhat flattened body; abdomen ending in long, or rather long, 

 jointed cerci. 



1. Occiput of the head small and hardly distinct from the vertex; first ventral 

 segment with four posterior processes; cerci short, robust, sLx-jointed, per- 

 forated at apex; ten spiracles. (Anajapyx) (PL 16, fig. 386). 



PROJAPYGID^ 



Occiput rather large and distinct from the vertex; first ventral segment with 



two posterior processes; cerci long, slender and apically imperforate; three 



spiracles. (Campodea.) (PI. 16, fig. 279.) CAMPODErD.ffi 



ORDER DICELLURA. 



{URATOCHEILA.) 



Rather delicate terrestrial insects with somewhat flattened 

 body, the abdomen ending in a pair of strong one-jointed forceps; 

 first ventral segment with two short styles and two submedian 

 hairy papillae. 



(Japyx) (PI. 16, figs. 382, 383) JAPYG1D.S 



CLASS COLLEMBOLA. 



Minute, wingless, springing insects; body sometimes clothed 

 with scales; abdomen consisting of six segments and never ter- 

 minated by caudal filaments or pincers-like appendages; ventral 

 tube always present; a forked leaping appendage usually present 

 beneath the abdomen. Eyes of degenerate compound type; 

 palpi vestigial; antennse with four to six joints; tarsi one-jointed; 

 no metamorphosis. 



ORDER ARTHROPLEONA. 



Body lengthened, subcylindrical ; the abdomen composed of 

 six free segments, the fourth segment often much lengthened; 

 heart with six pairs of ostioles. 



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