22 
BRITISH BEETLES. 
breadth of joints of the limbs, the degree of punctua- 
tion generally, the amount of pubescence, the greater 
or less elevation, depression, angulation or rounding of 
the thorax and elytra, the structure of the surface, and 
the sexual characters, being the chief points to be 
noticed. Species, also, that resemble each other 
very much on the upper side frequently differ con- 
siderably on the under surface. Occasional differences, 
owing to want of maturity, accidental abrasion, or 
slight varieties, — the frequent want of similarity in 
sexes of the same species, — and the absolute difficulty 
of seeing miuute specimens in the same light and level, 
do not tend to decrease the natural difficulties of this 
branch of the study. 
