310 



BULLETIN 63, UNITED STATES NATIONAL MUSEUM. 



obsolete upon the strong basal constriction, and the other line con- 

 tinning reactive to a greater degree, again may have diverged dichot- 

 oinously, evolving the tenehrosa strain, "with the sides of the pro- 

 thorax evenly or nearly arcuate from apex to base; the other being 

 the consohrina-parvicoUis ramus. ParricolJis is not only plastic, 



but prolific, populating the regions it inhabits with puzzling varia- 

 tions, many of them at the beginning of their incipient racial devel- 

 opment. In these forms the sculpturing is rather fine, abdomen not 

 coarsely sculptured, pronotal base quite strongly constricted, the pro- 

 thorax is broader and less strongly convex and more or less impressed 

 along the sides. 



The consohrina ramus apparently departed from an interesting 

 strain ; that is, incuUa, an insular species apparently, for if it be found 

 on the mainland it is rare ; in incidta the thorax is broad, very feebly 

 rounded at the sides, and scarcely at all sinuate near the base, with 

 the marginal bead strong and reaching the basal angles — these 

 characters in contrast to the more elongate eonsohi'ina, with narrower 

 prothorax which is distinctly constricted at base, the marginal bead 

 becoming a fine line upon the constriction, and the elytra more tuber- 

 culately sculptured. Here, again, are evidences of plasticity to en- 

 vironment. 



Let the student correlate the above characteristics with the genital 

 characters as presented below in the synopsis, and I believe the above 

 relationshi2)s will become more evident. 



SYNOPSIS OF GENITAL CHARACTERS. 



Males. 



Apicale of the cdeasoitlioro with a niediiui .sroove; sides scarcely arcuate. 



Ai)icah' without a uicdiau groove. 



Icconici. 



snoH'ii. 



trnchrofia. 



incuUa. 



eoiisohrina. 



hhnichurdii. 



neotomw. 



fuclmi. 



hornii. 



parricoUis. 



hopinngii. 



chrvicornis. 



scabrosa. 



cordata. 



pitnelioides. 



Apicale larger, sides more or less broadly siuuate, apex ai)pear 

 ing attenuate 



Apicale rather narrow; sides f(H>bly arcuate 



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