SCOLYTIDA. 83 
the secondary characters in 37 N.-American species, after careful dissection of the 
genitalia. 
He has been led to reverse many of those given by previous authors, and summarizes 
his conclusions thus: ‘‘ 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 former statement is quite true, 
but if the latter be so, an insuperable difficulty is thrown in the way of descriptive 
writers, who cannot examine the genitalia of more than a small proportion of exotic 
species. 
Secondary characters are by no means universal ; they have been overlooked or are 
entirely absent in such genera as Cryphalus, Hypothenemus, and Hypoborus, and many 
Hylesinids. In the Xylebori a special feature, not recorded in other subgroups, 
prevails, the males being dwarfed, subapterous, and otherwise structurally altered ; 
in the following remarks they are excluded from consideration. 
By the expression that such characters are found in any specified organ of a particular 
sex and species, it is meant that that organ varies in structure from the type common 
to the genus, group, or family, and existing in the opposite sex. 
The most frequent of such characters are :— 
Front. Less convexity, flattening, or actual excavation ; the presence of a polished plaque, 
tubercles, or carine. 
Denser or longer pubescence or villosity ; the presence of fasciculated hairs. 
Antenne. Greater development of the scape or club ; elongation of the funiculus. Presence of 
cilia or fimbrize on any part. 
Elytra. Stronger armature; greater depth of the apical excavation or sulci, or at least flattening 
of the apex. 
Abdomen. Flattening or greater concavity ; the presence of armature. 
Secondary characters are also found in the mouth-parts, tibie, &c., but are not 
yet known to be of common occurrence. 
In the subjoined Table (pp. 84-85) are analyzed the chief secondary sexual 
characters of about 80 species belonging to 28 genera, in which they have been 
correctly applied after dissection by Lindemann, Eichhoff, Hopkins, or myself. The 
species in which they have been determined is not given, as a rule; and it is intended 
to imply not that such characters are common to all species of a group or genus, but 
that when present they are confined to one sex without proved exception, unless such 
be mentioned. 
MM 2 
