THE CHARACTERISTICS OF INSECTS. 



2 33 



legs (Fig. 13). The leg has the form of an elongated trapeze, the 

 major base of which is often provided with spurs, while the crest 

 is covered with teeth or rigid hairs. The tarsus is composed of 

 joints, not exceeding and not always reaching five in number. 

 These short joints are of different forms. They are sometimes 

 furnished with fine balls of silk, a kind of brushes which aid in 

 standing or with suckers answering the same purpose. The 

 last joint of the tarsus, called the onychium, bears one or two 

 nails. The joints of the tarsi are generally distributed in equal 

 numbers upon all the legs of the insect ; but there are some- 

 times fewer on the middle and after limbs than on the fore 

 limbs. 



The arrangements we have pointed out hold with the walk- 

 ing insects ; with aquatic insects the rugosities of the joints are 

 smoothed down, the nails are blunted, and the legs are trans- 

 formed into ciliated paddles 

 that permit the animal to 

 move easily in the water. 



The abdomen consists of 

 a series of rings joined to one \ 

 another by a fine membrane ^Pli 

 which gives them great mo- ^ 

 bility. It is by means of this 

 disposition that the abdomens 

 of females when distended 

 with eggs attain such ex- 

 traordinary proportions. The 

 number of abdominal seg- 

 ments varies from six to nine. 

 The last ones are sometimes 

 transformed into accessories of the genital apparatus. The last 

 horny arch of the abdomen is called the pygidium, as in the tail 

 of the cockchafer. 



The cutaneous envelope of insects is usually of a dull, ruddy, 

 or pitchy color ; sometimes clearer, sometimes of a metallic ap- 

 pearance; but that which constitutes their richest livery is the 

 investment of their external skeleton. This investment is formed 

 of silks, felted hairs, spines, or thin caducous scales, the overlay- 

 ing of which composes most original designs. A moderate en- 

 largement is sufficient to give some species the appearance of 

 brilliant jewels ; seen under the lens, the Curculio imperialis, a 

 Brazilian beetle, appears like a real set of emeralds and diamonds. 

 Nothing is more interesting than to observe the fine pubescence 

 of our native weevils and the delicate scales of the coats of some 

 individuals. All these ornaments are, however, so fragile that 

 we only have to graze a butterfly's wing with the finger to scatter 



Fig. 14. Foot of a Fly. j>, pclotcs ; ff, nails. 



