Legs of Insects. 63 



edge of the seciDndary wings we often find hooks, to attach 

 them to the front wings (Fig. 4, j5, C, /4). 



The wings are moved by powerful muscles, compactly 

 located in the thorax (Fig. 15), the strength of which is 

 very great. The rapidity of the vibrations of the wings 

 when flight is rapid, is really beyond computation. Think 

 of a tiny fly outstripping the fleetest horse in the chase, and 

 then marvel at this wondrous mechanism. 



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

 ture insects, two on the lower side of each ring of the 

 thorax. These are long or short, weak or strong, accord- 

 ing to the habit of the insect. Each leg consists of the 

 following joints or parts: The coxa (Fig. 44, c), which 

 moves like a ball and socket joint in the close-fitting coxal 

 cavities of the body-rings. Next to this follow in order 

 the broad trochanter (Fig. 44, T), the large, broad femur 

 (Fig. 44, -F), the long, slinj tibia (Fig. 44, T), frequently 

 bearing strong spines at or near its end, called tibial spurs, 

 and followed by the from one to five-jointed tarsi (Fig. 44, 

 I, 2, 3, 4, 5). AH these parts move freely upon each other, 

 and w^ill vary in form to agree with their use. At the end 

 of the last tarsal joint are two hooked claws (Fig. 45), 

 between which are the pul villi, which are not air-pumpt 

 as usually described, but rather glands, which secrete ii 

 sticky substance which enables insects to stick to a smooth 

 wall, even though it be above them. The legs, in fact the 

 whole crust, are more or less dense and hard, owing to the 

 deposit within the structure of chitine. 



INTERNAL ANATOMY OF 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 strisB or cross- 

 lines, the same as do the voluntary muscles of vertebrates, 

 and are very beautiful as microscopic objects. The sepa- 

 rate muscles are not bound together by .1 membrane, as in 

 higher amimals. In insects the muscles aie widely distrib- 



