168 AMERICAN COLEOPTERA. 



Group VII. 



As already stated, Group VI of Horn will be included here. 

 Of the three species referred to it, desertorum is only a small 

 form of prosopis, and usually has the hind femora armed with 

 two denticles, while aureolus and paupercu his may have either 

 one or two denticles as was recognized by Horn, who tabu- 

 lated them in both groups. The number and size of the 

 femoral denticles is like all other characters subject to varia- 

 tion, which usually manifests itself as a reduction in size and 

 occasionally a complete loss of a denticle in the smaller in- 

 dividuals. More rarely an extra denticle may appear, as I 

 have observed in nzusculus and obtectus, where there are not 

 infrequently three present, though the normal number is evi- 

 dently two. Exiguus of the following group, though typically 

 with three denticles, shows often only two, and thus would 

 be referred to the present group, the tabular characters lead- 

 ing to floridcz, which indeed I am inclined to believe is really 

 not distinct from exiguus. 



The species of this group are about as numerous as in 

 all the others together. The form is never very thick and 

 cuboidal, and is usually distinctly more depressed and elon- 

 gate than in the other groups. The antennae are never flabel- 

 late or pectinate, rarely strongly serrate, and seldom reach 

 as far as the middle of the elytra ; they attain their greatest 

 development in pectoralis, bisignatus, macrophthalmus , distin- 

 guendtis, subserripes and inquisitus. The fifth and sixth elytral 

 striae are shortest in nearly all species, the only exceptions 

 among the species known to me being bisignatus, subserripes 

 and alboscutellatus, all of which are aberrant in the group in 

 at least one other respect. In quite a number of species the 

 first ventral segment of the male is sexually modified. In 

 perforatus and lobatus the surface is concave at middle and 

 produced apically in the form of a broadly rounded porrect 

 or slightly deflexed lobe. In aureolas, fraterculus, collusus, 

 perpiexus, pulhis, and presumably in mixtus, the central area, 

 which may or may not be distinctly flattened or slightly con- 

 cave, is margined at sides, and more especially at apex with 

 longer hairs, and there is near the base a small more or less 



