210 Proceedings of the Biological Society of Washington. 



Morphological Characters. 



The antennal club, eyes, head, thoracic segments, legs, wings, 

 abdominal tergites and sternites, spiracles and stridulating ac- 

 cessories, present many examples of parallel modification in 

 widely separated species, genera and families. The same is 

 true of many elements of the secondary sexual characters and 

 internal anatomy. 



The antennal funicle is perhaps the most important taxo- 

 nomic element of the Scolytoid beetles. It is one of the first 

 things to look for as a guide to the combination of characters 

 which distinguish the genus. While the same number of joints 

 may be parallel many times in connected, or disconnected 

 genera of the same subfamily, and in different subfamilies, 

 there must be, as applied to these beetles, the same number of 

 joints in all of the species of a genus. 



In the 221 genera, representing 16 subfamilies, the number 

 of joints in the funicle is paralleled as shown in the following 

 table: 



3 genera representing 1 subfamily have 1 joint. 



6 2 subfamilies " 2 joints. 



13 " " 4 " "3 " 



44 " 7 " " 4 



73 " " 9 "5 " 



31 " " 9 "6 " 



51 " " 9 "7 " 



The food, social and sexual habits, character of the brood 

 galleries, choice of host plants and distribution of genera and 

 species are all more or less rich in facts of taxonomic import- 

 ance and parallel development. 



In the social habits we find some features of special interest, 

 both in their relation to taxonomy and to parallel lines of 

 modification. In the relation of the sexes there is a wide 

 range of difference and progressive modification from simple or 

 unorganized, but intensive polygamy, towards a gradual reduc- 

 tion in the number of females and finally specialized monogamy. 

 We have here a remarkable case of social evolution which in a 

 like manner has been paralleled in that of the human species. 



There is a wide variation in the types or forms of the egg 

 and brood galleries within the families, subfamilies, the major 



