196 THE SCOLYTID BEETLES. 



fact almost every important element of the body, may be the bearer 

 of characters for distinguishing one or the other sex. 



It would appear that as a rule there is a certain degree of con- 

 stancy in the location and general appearance of a male or female 

 character within the hmits of a genus, but there are some remarkable 

 differences, and even reversals, even in the major and minor divisions 

 of a genus. In Dendroctonus, for example (Part I of this bulletin, 

 p. 73), the females of subdivision A are distinguished by the presence 

 of a transverse ridge on the anterior area of the pronotum, while in 

 subdivisions B, 0, and D this character is not present. In sub- 

 division B the elytral dechvity is more rugose in the female, in sub- 

 division C this is reversed, and in subdivision D there is no difference 

 in this respect. In some genera the pubescent or concave front is a 

 female character, while in other genera it is a male character. Other 

 reversals may not only occur in different, widely separated genera but 

 in the same genus. Therefore it is not safe to conclude that because 

 certain characters designate the female in one species this will hold 

 true for the other species of the same genus or for allied genera. This 

 can only be definitely settled by dissection, which can be done without 

 seriously mutilating the specimen if the abdomen is carefully removed 

 from the body and the sternites are remounted on a card point after 

 the examination is made. The presence of the chitinized sperma- 

 theca in the female and the presence of the chitinized elements of the 

 posterior section of the male organs are sufficient to settle the point, 

 even in old dried specimens. 



The lines of progressive variation or modification in secondary 

 sexual characters appear to range from absent and obscure to com- 

 mon and prominent. 



THE PUPiE. 



Comparatively very Httle study has been made of the pupse of even 

 our common species of Scolytoidea, and until a comprehensive study 

 has been made it is scarcely necessary to mention the characters in 

 connection with general taxonomy. The description and figures of 

 the pupa of Dendroctonus valens (Part I, pp. 53-57, figures 37-38; 

 synopsis, pp. 73-74, and descriptions, pp. 81-152) will serve as an 

 example of the general type, while the figures and terminology will 

 serve as a guide to future study. 



The writer has examined the pupae of quite a large number of 

 North American species and finds that there is quite a wide range 

 of variation, but no attempt has been made to analyze the taxonomic 

 characters except in the genus Dendroctonus, in which the form of 

 the head and the character of the frontal, tergal, lateral, pleural, 

 caudal, and femoral spines serve as important characters for identifi- 

 cation and classification and, when correlated with the adult charac- 

 ters, give the same or similar taxonomic result. 



