TfeE CANADIAN ENTOMOLOGIST. 275 



sexual characters given by those Speciahsts whom we recognize as the 

 best authority on the subject. 



There is considerable difference of opinion among Specialists regard- 

 ing the external sexual characters of species in the genus Platypus as 

 based upon those given by Dr. Chapuse in his Monographic des Platy- 

 pids. With a view of satisfying myself on this question, I dissected a 

 number of alcoholic and dried examples of male and female P. quadri- 

 dentatus and P. compositus. The results convinced me that the male and 

 female characters given in the description of these- two species are 

 reversed. 



The fact that descriptions of male and female Scolytids are based 

 largely upon the characters given by Chapuse causes me to question the 

 correctness of interpretations of the external sexual characters in other 

 genera. 



This led to the commencement of a systematic study of the sexual 

 characters of all the species of which I had sufficient material. A num- 

 ber of male and female examples of Xy Icterus retusus, Xyloterus bivitta- 

 tus, Xyleborus dispar, and Xyleboriis obesiis were first dissected and a 

 careful study of the male and female genitalia was made. I found that 

 the male organ, while exhibiting remarkable differences in the species of 

 the two genera, possesses certain peculiarities by which it can be readily 

 recognized, even in dried specimens. Guided by this, I continued the 

 investigation until male and female examples of thirty-seven species, 

 representing seventeen genera, were dissected. 



According to my interpretations, based upon the finding of the male 

 genitalia in the species examined, the sexual characters, as given by Le 

 Conte in Rhynchophora of America, North of Mexico, are wrong in ten 

 species out of five genera, and correct in ten species out of nine genera. 

 In fourteen species out of ten genera external sexual characters were 

 determined, which were previously unknown to me, and most of them are 

 probably new to science. In three species out of three genera, no dis- 

 tinctive or constant characters were observed by which the sexes could 

 be designated. 



While the external sexual characters appear to be constant with the 

 species in some genera, in others no particular character is possessed by 

 all of the species. In fact, what may be a good male or female character 

 in one species will be reversed in another species of the same genus. 



The greater development of the elytra and abdominal armatures is a 



