AMERICAN COLEOPTERA. 279 



most species with non-sulcate thorax. It, however, nearly or quite 

 fails in rohusta, longiclava, truncata and joicea, in which tlie terminal 

 joint is more pointed and feebly truncate in both sexes. In the spe- 

 cies with sulcate thorax there is but little sexual disparity in this 

 regard, the terminal joint being more slender and less broadly trun 

 cate at apex than in the sulcate series. 



There is a marked tendency throughout the genus toward pale- 

 ness in color; the under surface, head and thorax most frequently, 

 the elytra more rarely, becoming partly or entirely rufous or testa- 

 ceous. This tendency is more pronounced in the females, and in 

 certain species, fulgida and crotchii, the head, thorax and body 

 beneath are normally pale in this sex, the same parts being blackish 

 or piceous in the males. 



In antennal structure there is little variation in the genus. In 

 the few known specimens of picea these organs are 8 jointed ; in all 

 others they seem to be normally 9 jointed. In the single female of 

 robusta there are only eight joints, but as there are nine in the male, 

 I suspect this may be accidental. Such accidents are not rare in 

 the Lamellicornia, where the number of joints in the funicle is fre- 

 quently subject to an individual decrease through coalescence. The 

 antennal club in the male is normally subequal in length to the 

 funicle, and is about twice as long as in the female ; to this, however, 

 thej'e are three exceptions. In clypeata the male club is very short, 

 not differing appreciably from that of the female ; a most extra- 

 ordinary fact. In pallens the female club is unusually long, being 

 about equal to the funicle, a condition which is, however, in part 

 due to the shortness of the latter; males have not been seen. In 

 the male of longiclava the club is abnormally long, being sensibly 

 equal to the basal joint and funicle combined ; of this species fe- 

 males have not been seen. 



Geographically speaking, Dlchelonycha is widely dispensed, but 

 the genus is essentially a northern one; or more accurately, it is 

 nearly confined to the Boreal and Transition Zones,* which, with 

 the exception of the highlands of Pennsylvania and a narrow strip 

 along the Alleghany Mountains, reach their southern limits in the 

 Eastern United States in about the latitude of New York City and 

 the southern lake region ; but which in the Rocky Mountains and 

 Pacific regions extend entirely across the country. In the East, 

 ® See Merriam's Life Zones of the United States. 



TRANS. AM. ENT. SOC, XXVII. AUG., 1901. 



