212 



BULLETIN 63, UNITED STATES NATIONAL MUSEUM. 



beyond the middle of the dorsal plates, and the genital fissure is open 

 and fnsiform. 



Our species may be separated as follows : 



Species ecaudate. 



Elytra silicate, intervals more or less convex /(i.s7>i/«?j/-/.s. 



Elytra substriate, intervals flat sponsn. 



Species caudate. 



Dorsal surface of body not clothed with long, flying hairs cuudifcra. 



Dorsal surface clothed with long, flying hairs . loiigipiJostd. 



The female genital characters may be tentatively formnlated as 

 follows : 



Genital segment more or less quadrato-trapezoidal ; appendage flattened and 

 subtriangular. 



Dorsal plate oblong, sides parallel ; apical margin subtruncate sponsa. 



Dorsal plate irregularly oblong; apical margin more or less arcuate. 



hispilahris. 

 Genital segment more or less triangular ; appendage conical. 



Dorsal plate oblong, sides subparallel ; apical margin more or less oblique. 



caudifera. 

 Dorsal plate oblong-oval, sides arcuate; apical margin more or less arcu- 

 ate loiigipilosd. 



Genealogy. — An examination of the accompanying diagram will 

 elucidate the apparent relationships and lines of descent. The lines 



of divergence are apparently the ac- 

 quisition of the elytral catida on the 

 one hand and the elytral apices re- 

 maining indifferent on the other; 

 in the former the development of an 

 .scu]ptffi8 unusual degree of pubescence with 

 the disappearance of the femoral 

 teetli are very striking morpholog- 

 ical coincidents along the lines of 

 correlated characters. 



Tracing the divergencies along 

 the ecaudate ramus of the genea- 



Dentipes Group, Section A, Subgenus logical tree, it will appear as if 



sponsa dn'erged, retaining a com- 

 paratively simple form of elytral sculpturing and has apparently 

 reacted less than /lispilahris to its environment. 



Hispilahris has, indeed, undergone a wonderful amount of differ- 

 entiation into a number of incipient races, primarily by the sculp- 

 turing remaining comparatively simple with rather fragile integu- 

 ments, and, secondarily., by a more decided character of sculpturing 

 having been acquired along with an increased thickness of the exo- 

 skeletal wall. Tn the former instance forma typica and nnpta were 

 evolved, the latter by increased ventricosity of the body; in the latter 



Sponsa 



longipilosa 



Fig. 4. — Genealogical diagram of the 



