Legs of Insects. 63 
edge of the secondary wings we often find hooks, to attach 
them to the front wings ve 4, B, C,z). 
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 reaHy 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, 2, 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, 7), the large, broad femur 
(Fig. 44, /), the long, slim tibia (Fig. 44, 7), 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). ‘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. 45), 
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 smootn 
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 striae 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 a membrane, as in 
higher amimals. In insects the muscles are widely distrib- 
