3090 THE JOINTED ANIMALS 



each of the joints is short and bead-like. 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 occurrence 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 consid- 

 ered probable that certain minute pits scattered over the surface of the antennae, or 

 crowded together on special areas, are in some way coiected 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 le'ast the}' possess this faculty. Every one has heard of 

 the deathwatch beetle (Anobium), which lives in old furniture and woodwork 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 (Megalopinee} 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 backward and for- 

 ward over the ribbed surface of the mesonotum. In other beetles the stridulating 

 area may be either on the upper surface of one of the hinder segments of the ab- 

 domen, 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 

 accordance with their running powers, we find that their legs, though generally 



