126 
INSECTS. 
The antennae are said to be clavate when thickened at the extremity, in the form 
of a knob or club; lamellate when three or more of the terminal joints spread out 
in broad processes which lie flat upon one another; serrate, when the joints have 
on one side short angular processes like the teeth of a saw ; pectinate or comb-like, 
when the processes are fairly long and stand out nearly at right angles; or 
flabellate, if the processes are proportionately very long. These are some of the 
chief types of antennae met with in the Coleoptera; others of less frequent occur¬ 
rence will be mentioned when we come to treat of the different families. The sense 
of smell is undoubtedly very acute in a great many beetles, as anyone acquainted 
with their habits could easily testify; and it is considered probable that certain 
minute pits scattered over the surface of the antennae, or crowded together on 
special areas, are in some way connected with this sense. Though it is not so easy 
to prove that beetles can hear, it seems hardly open to doubt that in some cases at 
least they possess this faculty. Every one has heard of the death-watch beetle 
( Anobium ), which lives in old furniture and wood-work of houses, and makes a 
noise like the ticking of a watch. This little beetle produces the noise by hammering 
against the wood with its head, and apparently does so for the purpose of attracting 
its mate, who replies by making a similar tapping sound. It is easy by imitating 
their sounds to get the beetles to answer back; so that here at least there is some 
evidence that these insects are endowed with the faculty of hearing. Many other 
beetles are able to make sounds, which though not nearly so intense as the chirping 
of the crickets and grasshoppers, and not usually confined to one sex, are produced 
somewhat after the same manner by the friction of one part of the body over 
another. In beetles the sound sometimes arises from the rubbing of the hind-legs 
against the edge of the elytra, but in most cases it results from the rubbing of an 
edge over an adjacent area which is crossed like a file by a number of fine parallel 
ridges. This stridulating area is in some beetles placed on the upper side of the 
back part of the head, or on the gular surface underneath, so that when the head 
moves in its socket the upper or lower edge of the prothorax, as the case may be, 
scrapes along the file and thus gives rise to the sound. The prothorax of beetles 
is, as we have already stated, freely articulated with the mesothorax. Its dorsal 
arch or pronotum ordinarily covers over the whole of the mesonotum, with the 
exception of the small piece known as the scutellum; but when the prothorax is 
bent down, a considerable part of the mesonotum in front of the scutellum comes 
into view. It is on this part that the stridulating area of most of the longicorns 
and of some phytophagous beetles ( Megalopinon ) is situated. These insects make a 
sort of squeaking noise—which is sometimes fairly loud—by rapidly bending the 
prothorax up and down, and so causing its hind edge to move backwards and 
forwards over the ribbed surface of the mesonotum. In other beetles the stridu¬ 
lating area may be either on the upper surface of one of the hinder segments of 
the abdomen, or on the sides of one of the anterior segments; the sound being 
produced in the one case by the friction of the area against the edge of the elytra, 
in the other by that of the posterior thighs against the sides of the abdomen. 
Beetles are among the most active of insects when on the ground, and, in accord¬ 
ance with their running powers, we find that their legs, though generally slender, are 
strong and well developed. But in certain groups, where the habits and environ- 
