90 AMERICAN COLEOPTERA. 



The unique above referred to is from the valley of the Colorado 

 River. 



Group xii. variegatum. 



Maxillpe with the outer lobe biarticulate ; frontal grooves single, 

 parallel or rarely very feebly convergent ; eyes large, prominent. 

 Elytra distinctly striate, witli at least the two inner stride entire ; 

 humeri rounded ; dorsal punctures two, situated on the third interval. 



This is the largest group of the genus and the most difficult of 

 study. Many of the species resemble each other very closely and 

 exhibit a large amount of variation, especially in color and elytral 

 markings. As a result the number has been needlessly multiplied, 

 the characters on which several were based becoming evanescent 

 when a large series of specimens is studied. 



In more than half of the species the head is alutaceous. In fact, 

 I had hoped to be able to make use of this character in subdividing 

 the group, as suggested by LeConte. This, however, has been found 

 to be impossible, as it would not only involve the separation of spe- 

 cies otherwise very closely allied, such as dorsale and postfasciatum, 

 but in some, as for instance versicolor, the head varies from very 

 finely to not at all alutaceous. No other character has been found 

 which could be made use of for its subdivision without, at the same 

 time, destroying marked affinities. 



The group, therefore, is unwieldy from its size, and it is impossible 

 to place the species in natural order in a linear arrangement. It is 

 hoped that the following table will affi)rd some assistance to the 

 student in the determination of our species, which follow in the text 

 in what seems to be the best order for cabinet arrangement : 



Striae of elytra i)unctate. 2. 



Striae of elytra impunctate. 



Broad, feebly convex; testaceous with the occiput, apex at middle and base of 

 thorax, and cloud-like spots on the elytra dusky; thorax subquadrate, 

 slightly narrower at base than ajiex, hind angles not carinate ; legs testa- 

 ceous. Length .20-.24 inch tigriiiiini Lee. 



2. Thorax narrower at base than apex 3. 



Thorax not perceptibly narrower at base than apex 12. 



3. Form depressed, strise of elytra entire 4. 



Form more or less convex 5. 



4. Head alutaceous. 



Thorax cordate, much narrower at base than apex, sides distinctly sinuate 

 behind. 

 Head and thorax coarsely alutaceous, cupreo-geneous, elytra testaceous, with 

 bronzed or nearly black markings ; thorax nearly twice as wide as long; 

 base of antennte and legs testaceous. Length .22-.25 inch. 



cordatuiu Lee. 



