56 MANUAL OP THE APIARY. 



are really beyond computation. Think of a tiny fly outstrip- 

 ping the fleetest horse in the chase, and then marvel at this 

 ■wondrous mechanism. 



The legs (Fig. 2, g, g, g) are six in number in all mature in- 

 sects, two on the lower side of each ring of the thorax. 

 These are long or short, weak or strong, according to the habit 

 of the insect. Each leg consists of the following joints or 

 parts : The coxae (Fig. 24), which move like a ball and socket 

 joint in the close-fitting cozal cavities of the body-rings. 

 Next to these follow in order the broad tracanter, the large, 

 broad femur (Fig. 2, g', 1), the long, slim tibia (Fig. 2, g', 2), 

 frequently bearing strong spines at or near its end, called 

 tibial spurs, and followed by the from one to five-jointed 

 tarsi (Fig. 2, g', 3, 3, 3, 3, 3). All these parts move freely 

 upon each other, and will vary in form to agree with their 

 use. At the end of the last tarsal joint are two hooked 

 ■claws (Fig. 2, g', 4), between which are the pulvilli, which 

 are not air-pumps as usually described, but rather glands, 

 which secrete a sticky substance which enables insects to 

 stick to a smooth wall, even though it be above them. The 

 legs, in fact the whole crust, is more or less dense and hard, 

 owing to the deposit within the structure of a hard substance 

 known as chitine. 



INTERNAL ANATOMY OP INSECTS. 



The muscles of insects are usually whitish. Sometimes I 

 have noticed quite a pinkish hue about the muscles of the 

 thorax. They vary in form and position to accord with their 

 use. The mechanism of contraction is the same as in higher 

 animals. The ultimate fibers of the voluntary muscles, when 

 highly magnified, show the striae or cross-lines the same as 

 do the voluntary muscles of vertebrates, and are very beauti- 

 ful as microscopic objects. The separate muscles are not 

 bound together by a membrane as in higher animals. In in- 

 sects the muscles are widely distributed, though, as we should 

 expect, they are concentrated in the thorax and head. In in- 

 sects of swiftest flight, like the bee, the thorax (Fig. 7, a, a, a) 

 is almost entirely composed of muscles ; the oesophagus, 

 which carries the food to the stomach, being very small. At 

 the base of the jaws, too, the muscles are large and firm. 



