18 GENERAL ZOOLOGY 



are the katydids (Fig. 7), large green insects of arboreal 

 (tree-dwelling) habits, found in the eastern and central 

 United States. They afford an illustration of protective re- 

 semblance, — a term which is used to cover those cases in 

 which an animal possesses colors or shape which harmonize 

 with its environment (surroundings), or with some par- 

 ticular object in the environment, thus affording protection 

 against enemies. In the case of katydids the whole body 

 is green and the wings are thin and veined like a leaf. The 

 well-known note from which the name "katydid" is derived 

 is produced only by the male, and is made by rubbing the 

 base of one of the first pair of wings against the other 

 anterior wing. An auditory apparatus is found in both 

 sexes at the base of the front tibiae, not on the abdomen as 

 in the short-horned grasshoppers. The female has a long 

 sword-like ovipositor (Fig. 6) with which the eggs are thrust 

 in overlapping rows into the bark of twigs. The common 

 meadow grasshopper (Orchel'imum, Fig. 6) gives a good 

 idea of the appearance of a long-horned grasshopper. 



Crickets. The crickets (Fig. 8, A) resemble the grass- 

 hoppers in the possession of long, slender antennae, but 

 differ from them in having the anterior wings overlapping, 

 instead of meeting in a ridge along the median line of the 

 back. They are widely distributed over the earth, and are, 

 as a rule, nocturnal in their habits. They feed mostly on 

 vegetable matter, though at times they destroy clothing. 

 Our native species live in the fields beneath sticks and 

 stones. The house cricket of Europe (Gryl'lus domes'ticus) 

 has spread into many parts of the United States. This is 

 the species famous in song and story. Its well-known chirp 

 is made only by the male. The principal vein on the ventral 

 surface of each anterior wing is thickened into a rasp-like 

 structure (Fig. 8, B) ; on another part is a hardened por- 

 tion called the scraper. The noise is produced by raising 



