30 
BRITISH BEETLES. 
The head, bearing the eyes, antennae, and organs of 
mastication, &c., is the first to be considered. The 
accompanying cut of the 
head of a Water-beetle will 
show the chief points to be 
noticed on the upper side : 
here, a is the labrum or 
upper lip ; b, the clypeus or 
shield of the mouth, often 
bearing tubercles or even 
horns ; e and d are the man- 
dibles or upper jaws (these 
are dissected out in the 
ficrnrp and is ‘TPVfvrspd^ ■ Upper side of head of T). margin 
ngure, dUU u lb avuseu; , iialis {highly magnified). 
e e, the eyes ; /, the base of 
the antennae ; g, the vertex or crown, and h the 
occiput. 
The mandibles are hard and sharp, often (as in the 
male of the Stag-beetle) very much developed. The 
eyes, which are composed of many facets, situated on 
the side of the head, and usually large, ai’e normally 
two in number, being however in some cases aberrant ; 
for instance, in Dorcus (the small Stag-beetle), each 
eye is almost divided into two, being interrupted by 
the lateral ridge of the head ; and in the Gyrini (the 
“ Whirlwigs ”), it is distinctly divided by a deep broad 
channel, containing the antenna, so that tho insect is 
four-eyed, having two on the upper and two on the 
tinder surface, — an admirable structure for species that 
pass their lives on the top of the water, and need extra 
sharpness of vision, partly to save themselves from foes 
above, and partly to detect their own food below. 
There are also in some few beetles two ocelli, or addi- 
ng. 3. 
