70 GEO. H. HORN, M. 1). 



Last Ventral Segment. — In all our species the last ventral 

 segment is emarginate in the male, but variable in extent among the 

 species, from the deep quadrangular ncjtch of rjemmata (180) or 

 acufipeiuiis (190) to the feeble arcuate truncation of chrijmela (229), 

 seitH/it{2o4) or atrifcisciata (240). It is not often that the disc is 

 carinate in the male, and then the carina is short, and never entire, 

 as in the female. The disc is more commonly broadly sulcate at 

 middle as in Merkelii (185) or aentipe)tiiis (190). The last ventral 

 of the female is rarely as deeply emarginate as in its male, analis 

 (210), usually much less so and quite often truncate as in acvtipennis 

 (191) or geimnata (181), sometimes more or less sinuate as in chri/soela 

 (230), scihda (235) or utrifasciata (241). The tridentate form of 

 apex is rare, libonotl (196). Many modifications of the emarginate 

 type will be observed in the sketches. The disc is often strongly 

 carinate in the female, the carina extending from the base to the 

 apex as in octocola (9), gemmata (181) or Merkelii (186). The last 

 dorsal segment often differs in the sexes, principally in sculpture, the 

 punctuation in the female being coarser and deeper than in the male. 

 It will, however, be observed that in feiuomta the last dorsal of female 

 is carinate at middle, a deep fovea on each side. 



From the preceding remarks, which have been condensed as much 

 as possible, it will be seen that modifications of a purely sexual im- 

 port occur in many portions of the body, which can be utilized in 

 more accurately defining species. The form, color and sculpture of 

 species are often so variable that two specimens of different species 

 will more closely resemble each other superficially than other indi- 

 viduals of the species to which they belong. This is especially ob- 

 servable in the trinervia series, where recourse to sexual characters is 

 the only means of separating the closely allied members. 



The species of Chrysobothris are so numerous in our fauna that 

 they may be best understood by dividing them into groups. The 

 primary division adopted is practically that i)roposed by Dr. LeConte 

 in his Revision, with such modifications as have been rendered neces- 

 sary by the increased material. It nnist not be supposed that these 

 " groups" are such natural divisions that they have equal value, they 

 are merely adopted for convenience, and those who study the species 

 will find many points of resemblance between members of widely 

 separated grou])s, e. g. femoratu and ^ie.vsi g imta. 



