242 ELEMENTARY ZOOLOGY. 



reality, for these animals are a chief source of food for fishes and 

 other water animals. 



There are many marine Crustacea related to cyclops. Many of 

 them are parasitic, infesting the skin, gills, the intestine, and other 

 organs of the larger invertebrates, the fishes and whales. 



258. The Relatives of the Grasshopper (Insecta). 

 This division of arthropods is in contrast with the Crus- 

 tacea in the fact that the insects are chiefly air-breathing. 

 The insects have typically four pairs of jointed appen- 

 dages in the head (one pair of antennas and three pairs of 



FIG. 89. Sminihurus hortensis a spring-tail. X 35. From Folsom's Ento- 

 mology. 



Questions on the Figure. Consult other texts and discover the 

 habits and special adaptations of these insects. 



mouth parts), and three pairs of legs on the thorax. The 

 name Hexapoda is sometimes given them because of this 

 regularity in the number of legs. There are more species 

 of insects than of all the rest of the animal kingdom put 

 together. Included here are the wingless spring-tails, 

 the fleas, the May-flies, the dragon-flies, the cricket, the 

 katydid, the cockroaches, lice, plant-lice, bugs, beetles, 

 flies, gnats, mosquitoes, butterflies, moths, ants, bees, 

 and wasps. All the grubs, caterpillars, maggots, and 

 the like, are larvae of this division. 



259. Wingless Insects. While most insects have wings, 

 there are some groups which do not. Among these are 



