FIRST LESSONS IN ZOOLOGY. 



is held in front. They are long and narrow, with a number of 

 raised ridges called veins, a few larger ones extending along the wing, 

 and the smaller ones across. 



The hind wings are broad and thin, so as to be transparent, and 

 are veined like a leaf. They are folded up like a fan, and, when 

 spread out, the locust can sail all day in the air, borne along by the 

 wind. Most locusts fly but a short distance, but the migratory lo- 

 cust of Eastern countries and the Rocky-Mountain locust of the Far 

 West have longer wings, and can thus fly farther. 



Fig. 100. Cross-section through the thorax of 

 a butterfly. a b, muscles for raising, r rf, 

 for drawing downward and inward, the legs; 

 d, eutothorax arising from the sternum, k, 

 st ; ny, wing- vein; y, fulcrum, or turning- 

 point; c /(, muscles for lowering, It J, for 

 raising, the wing; i k and m , muscles for 

 lowering, I o p, for raising, the dorsal plates. 



FIG. 101. Diagram of muscles of 

 an insect's leg. Besides the mus- 

 cles at the insertion of the limb 

 for raising and lowering it, in 

 the trochanter (tr) is a muscle 

 for rotating the leg; i, for 

 stretching the tibia (M<); !, flex- 

 or of tibia; o, flexor of the tar- 

 sus; m, retractor of the tarsus 

 and claws (cl). 



Now we are ready to look at the head. First, as to the eyes. There are 

 two kinds: a pair of large compound eyes, one on each side of the head. 

 In front are three little shining points (Fig. 99, o), which are the simple 

 eyes. They are rather hard to see without a lens, especially the upper 

 ones, which are partly overhung by a ridge; they are arranged in a 

 triangle, the third one forming the apex of the triangle, and situ- 

 ated between the antennae, as seen in Fig. 99, o. The feelers are 

 called antenna?, from their fancied resemblance to the antenna or 

 yard of a Roman vessel. They are long and slender, and com- 

 posed of about twenty joints, the number varying in different kinds 



