BRANCH ARTHROPODA; CLASS 1NSECTA : THE INSECTS *93 



eludes the cockroaches, crickets (fig. 56), katydids and 

 green grasshoppers, the walking-stick or twig insects, the 

 praying mantis and others. 

 The members of this order all 

 have an incomplete metamor- 

 phosis, and in all the mouth- 

 parts are fitted for biting and 

 the fore wings are more or 

 less thickened and modified to 

 serve as covers or protecting 

 organs for the broad, plaited, 

 membranous hind wings, which 

 are the true flight organs. The 

 hind legs of locusts, grasshop- FIG. 56. The house cricket, 

 pers, crickets, and katydids are ^) and female (*) ( From 

 very large, and enable the in- 

 sects to leap; the legs of the cockroaches are fitted for 

 swift running; the fore legs of the praying mantis are 

 fitted for grasping other insects which serve as their food, 

 and the legs of the walking-stick (fig. 162) are long and 

 slender and fitted for slow walking. The shrill singing of 

 the crickets and katydids and the loud "clacking" of 

 the locusts are all made by stridulation, that is, by 

 rubbing two roughened parts of the body together. The 

 sounds of insects are not made by vocal cords in the 

 throat. The male crickets and katydids (for only the 

 males sing) have the veins of the fore wings modified so 

 that when the bases of the wings are rubbed together 

 (and when the cricket or katydid is at rest the base of 

 one fore wing overlaps the base of the other) a part of 

 one wing called the ' ' scraper ' ' rubs against a part of the 

 other called the "file" and the shrilling is produced. 

 The sounds of locusts are produced by the rubbing of 

 the inside of the hind leg against the outside of the fore 

 wing when the insect is at rest, or by striking the front 



