2*76 THE CANADIAN ENTOMOLOGIST. 



good male character in some species, but not in others. The frontal con- 

 cavity is a good male character in some genera, but is reversed in others. 

 The flattened or concave front fringed with long hairs is a good male 

 character in some species, but is of no value in others, as we have found 

 it either absent or reversed in species of the same genera. Size and 

 colour appear to be of no value except in Xyleborus, where" the male is, 

 as far as known, very much smaller and usually paler than the female. 

 Long hairs or bristles on the antennal club appear to be a good female 

 character in Monarthrum and Gnathotrichus. The long silky hairs with 

 curved points on the tibia and tarsus of male Xyloterus politus are rather 

 a remarkable and unique sexual character. Frontal elevations, depres- 

 sions, lines, channels and punctures are good sexual characters in some 

 species, while the same thing is of no value in other species of the same 

 genus. Thus, it will be seen that the external sexual characters are by no 

 means constant among the species, and that it is not safe to conclude 

 that because one species has a well-marked and known male or female 

 external character, that other species belonging to the same genus will 

 necessarily show the same character. It is my opinion that the sexes of 

 no species of Scolytidte should be characterized without previously 

 dissecting one or more examples of both sexes. 



The male genitalia are composed of certain horny parts, the form of 

 some one or more of which is usually characteristic to the nearly related 

 species of a genus, but a wide difference in the form of all of the parts 

 exists in species belonging to different genera. To characterize the 

 different forms by descriptions and drawings will require more time 

 than I have, as yet, been able to devote to this subject. It appears to me, 

 however, that further study in this line is necessary in order to approach 

 anything like a perfect and natural classification of the Scolytidaa, and I 

 hope to be able to contribute additional information upon this subject in 

 the future. 



Below, I submit a list of the species I have examined, and give the 

 sexual characters as I have interpreted them. As previously stated, these 

 conclusions are based upon the finding, in individuals of each species, a 

 peculiar structure composed of numerous horny parts, which is evidently 

 the male generative organ. The only room for doubt, in my mind, is in 

 the bare possibility of an ovipositor composed of horny parts being 

 possessed by the female of any of the species. The fact, however, of the 

 numerous examples dissected, where the presence of the ova left no doubt 



