XYLOPHILUS. 167 
rarity of these insects is well known: they require special working for, and are not 
often obtained by chance collecting. So far as my own observations go, they are, in 
Central America, chiefly found in oak-woods, at elevations of from 3000 to 8000 feet ; 
a considerable number of those collected by myself were beaten from the decaying 
branches of oaks. The numerous genera and subgenera that have been proposed by 
various authors are based solely upon European species, some of them upon single 
species only, and upon slight differences in the form of the antenne or eyes. ‘Three of | 
these, Phytobenus, Euglenes, and Aderus, have better claims than the others. These 
differences, however, are of specific rather than generic value. Huglenes and Phytobenus 
are not represented in Central America, but are replaced by other groups or subgenera 
of equal value, of which X. flabellatus and X. lacertosus may be taken as typical 
examples. The eyes in the Central-American species vary greatly in size (sometimes 
reaching the base of the head, sometimes distant from it), in the extent of the emar- 
gination (from very deeply emarginate to entire), and in the amount of pilosity (from 
densely pubescent to apparently bare *). The antenne also vary considerably : in the 
males of some species they are flabellate, or have a long apical joint; in others the 
intermediate joints are transverse in the female; one, X. tantillus, has the second and 
third. joints very short and subequal. The hind femora are often incrassate or clavate 
in both sexes, sometimes incrassate in the male and slender in the female. The sexual 
distinctions existing in many species in the form of the tibiz, femora, eyes, or antenne 
are very remarkable; and in this respect Xylophilus is one of the most interesting 
genera of the whole of the Heteromera. The peculiar pouch-like excavation of the 
hind femora of the males of X. fragilis, X. unifasciatus, X. sericeus, and X. bicolor, 
and the excavate, ciliate, and broadly dilated hind femora of the males of X. lacer- 
tosus, X. forticornis, &c., are especially noteworthy. 
In some of the Central- and North-American species the general shape is more 
elongate and Anthiciform, and in these the sexual distinctions are less marked. All 
are very fragile and difficult to obtain in perfect condition. 
The earlier stages of many Xylophili are, no doubt, passed in rotten wood, especially 
in that of various species of oak. : 
The following table will assist in the identification of the Central - American 
species :— 
‘Third antennal joint longer than the second (subequal in X. humeralis, X. curvipes, 
X. flavitarsis, and X. v-notatus), the two together much longer than 
the fourth. 
Sides of the thorax not dilated in front nor compressed at the middle ; 
eyes large or small, often larger and more approximate in the male 
(in some species occupying the whole of the side of the head, in 
* Under the microscope short fine hairs are visible between the facets. © 
