NORTH AMERICAN COLEOPTERA. 211 



tural characters in coniinon, show such modifications of the ehiw 

 that some of the species o4" Listrochelus might in one or even both 

 sexes be called Lachnosterna, while others have absolutely simple 

 claws. Tlie pectinate claw which should be characteristic of the 

 genus is possessed by not more than half the species, and even then 

 by the males alone. 



While the claws of Lachnosterna do not vary to the extent shown 

 in Listrochelus, there are important modifications. The usual form 

 is that in which there is a median tooth, and in probably the majority 

 of cases the tooth is longer and stronger in the females. In nearly 

 all the species of the aberrant groups (I to III and XII to XVIII) 

 the tooth is intra-median and small, although in many of the females 

 the tooth is median and strong. In one species the tooth is distinctly 

 in front of the middle (hirtlve)drls). There is no special form of 

 claw coincident with the modifications of structure of the hind tibial 

 spurs. 



A curious monstrosity (?) is shown by the outer anterior claws of 

 the male of veheniens (PI. iii, fig. 9, a, b, c), in which there is a small 

 additional tooth between the apex and the normal tooth. From 

 what we know of genera at present existing, this structure is prob- 

 ably a remnant of some type now extinct. 



We owe to Dr. LeConte the observation that two primary series 

 exist in Lachnosterna: first, those in which the posterior tibial spurs 

 of the male are both free and movable ; second, those in which the 

 inner spur is fixed, while the outer alone is movable. 



In the fii'st series the last abdominal segment is short, sometimes 

 almost linear, and the tooth of the claws usually intra-median, at 

 times almost basal. 



In the second the last ventral is longer, in fact nearly as lono- or 

 even longer than the preceding segment, and the tooth of the claw 

 median. 



These characters are by no means constant in the two series. The 

 length of the last ventral segment in the first series is subject to such 

 variation that, from the linear form, it approaches very closely to the 

 length observed in many of the si)ecies of the second series. Nor is 

 the position of the tooth on the claw constant, as in very many 

 females the tooth may be strong and median, while in the males it 

 is smaller and within the middle. 



In the table the structure of the male hind tibial spurs has been 

 taken as a character of first importance, as there is here no variation. 



