COLEOPTERA. 
I2 5 
the intervention of a short flexible piece known as the epistome—the upper lip 
(labrurn) is attached. Running along the middle of the under side of the head 
there is a piece, generally marked off by a line on each side, which in its posterior 
part is named the gula, and in front the submentum. The submentum—sometimes 
prolonged beyond the margin of the head in the form of a peduncle—gives attach¬ 
ment to the lower lip (labium), which consists of a basal piece of variable size and 
form called the mentum, and a terminal part, the ligula. The latter usually bears 
two lobes (the paraglossae) at its extremity, while from its base, known as the 
hypoglottis, the labial palpi arise. Between the labrum and labium lie the 
mandibles and maxillae. The mandibles are strong biting jaws, and are attached 
to the sides of the head by pivot-like joints, which permit only of lateral move¬ 
ments. They are often much larger in the males than in the females, and in the 
males of some forms such as the stag-beetles, attain monstrous proportions. Each 
of the maxillae consists typically of a stem, composed of two pieces—cardo and stipes 
—with a four-jointed palp attached to the outer and two lobes to the inner side of 
the free end of the stipes. Except in the larval state, beetles rarely possess those 
eyes with a single lens which are known as ocelli. The compound eyes, on the 
other hand, are generally large and well-developed, but vary considerably in form, 
and in the size and number of their facets. They are often simple in outline, 
sometimes slightly notched in front and reniform, or the notch may extend more 
deeply and divide the eye into two distinct lobes. Each eye may even be 
completely divided into two parts, more or less widely separated from one another; 
so that some beetles appear to have four eyes instead of two. This appearance is 
very strongly marked in certain water-beetles, in which one part of each eye is on 
the upper, and the other on the under side of the head. The eyes of some beetles 
look coarse and granular, while in others they appear quite smooth and glassy¬ 
looking, owing to the small size and slight convexity of their facets. Among the 
longicorn beetles, it is generally found that in the nocturnal species the eyes are 
coarser and more granular than in those species which fly during the day; so that 
the size of the facets seems to have some relation with the conditions of light 
depending on the habits of the insects. But this curious fact does not, so far as we 
know, apply to any other family of beetles. Exceptionally also it is found among 
beetles that the facets in the upjrer part of the eye are different in size to those on 
the lower part. The antennae of beetles are scarcely less important in their 
functions than the eyes. They are in most cases sensitive to touch, and there is 
reason to believe that these organs are also the chief seat of the senses of smell 
and hearing. They appear under a variety of different forms, some of which, 
while subject to minor modification, are pretty constant throughout certain large 
groups of beetles, and thus account for the names, Clavicornia, Lamellicornia, etc., 
given these groups. As a rule the antennae, no matter what their length, are made 
up of eleven joints or segments; but this number may be increased, in some cases 
to thirty or forty ( Rhipicera ), and even to as many as fifty (in the Longicorn genus 
Polyarthron), or it may be reduced even to so low a number as two (in Platy- 
rhopctlus). When the joints are more or less cylindrical in form, the antennae may 
be either filiform, if of nearly uniform thickness throughout, setaceous it they taper 
towards the extremity, or moniliform if each of the joints is short and bead-like. 
