170 THE SCOLYTID BEETLES. 



throughout the minor groups to the species, except in a few cases, 

 is of httle or no importance. 



The complete opposition in the characters of the apical angles of 

 the tibia, as shown in the subdivisions, is of special interest. There 

 is no apparent explanation on any theory of use or natural selection, 

 but it does appear to signify widely diverging lines of descent in 

 which this reversed element in the two subdivisions has remained 

 as the dominant and distinctive character. 



FAMILY CHARACTERS. 



In the classification of the famihes Ipidse and ScolytidaB into sub- 

 famiUes the principal characters used to distinguish the divisions 

 are found in the head (2)^, pronotum (4), and tarsi (2). 



The subdivisional characters are found in the antenna (2), tibia (2), 

 and abdominal sternites (2). 



The sectional characters are found in the antennae (2), eyes (2^, 

 pronotum (2), tibia (4), and form of body (2). 



The subfamily characters are found in the pronotum (4), antennae 

 (2), seventh abdominal sternite (2), elytra (2), and third tarsal 

 joint (2). 



It wiU be seen that in the classification of the two families into 

 subfamihes the principal characters are found in the head (8), pro- 

 notum (10), and tibia (7). . 



SUBFAMILY CHARACTERS. 



In the classification (in manuscript) of the 16 subfamilies of Ipidse 

 and Scolytidse into genera the principal character-bearing parts for 

 the divisions, subdivisions, and sections are as follows: 



Divisions: Head (1), antennal club (3), funicle (3), eyes {^), epis- 

 toma (2), maxiUa (1) — total for head (14); pronotum (5), tarsi (3), 

 and elytra (2) . 



Subdivisions: Antennal club (5), eyes (4), funicle (2), epistoma (1), 

 maxilla (1) — total for head (13); third tarsal joint (2), anterior 

 coxae (3), seventh abdominal sternite (2), and pygidium (2). 



Sections: Antennal club (4), funicle (2), eyes (1) — total (7). 



It will be seen that in the classification of the subfamilies the 

 characters are found in the head (35), tarsi (7), pronotum (5), 

 elytra (4), cox« (3), seventh abdominal sternite (3), pygidium (2), 

 and tibia (1). 



Suhsections and series to genera: The dichotomous characters of the 

 subsections and series and the distinctive characters of the genera 

 are as foUows: Antennal club (138), funicle (110), scape (7) — total for 



o The number folio-wing the name of a structure indicates the relative importance 

 or the number of times it figures in the dichotomy. 



