ARTHROPODS AND MOLLUSCS 157 



seventeen to twenty joints. They live in warm regions, 

 some growing to be very large, as long as twelve inches or 

 more. The "bite" or wound made by the poison-claws is 

 fatal to insects and other small animals, their prey, and 

 painful or even dangerous to man. The popular notion 

 that a centiped "stings" with all of its feet is fallacious. 

 It is recorded by Humboldt that centipeds are eaten by 

 some of the South American Indians. 



Insects (class Insecta). Insects are the most familiar 

 and abundant of land animals, and number more species 

 than are known of all other kinds of animals together. 

 Nearly 400,000 different species of living insects have so 

 far been found, and thousands of new ones are discovered 

 each year. Beetles, moths and butterflies, flies, wasps, bees 

 and ants, dragon-flies, plant-bugs and grasshoppers are to be 

 found in the vicinity of any schoolroom, and the interesting 

 habits of insects, their great variety and abundance, and the 

 readiness with which they may be collected, kept alive, and 

 studied, make them unusually fit animals for the special 

 attention of beginning students of zoology. 



Our studies with the grasshopper, mosquito, and cater- 

 pillars have already made us acquainted with the elementary 

 facts concerning insect body-form, structure, and life- 

 history, and elsewhere in this book are accounts of the 

 special relations of insects to flowers, to other animals and 

 also to man. 



Insects are classified into various groups called orders, 

 of which all the beetles constitute one, the moths and butter- 

 flies one, the two-winged flies one, the ants, bees, wasps, 

 etc., one, and so on. But to learn much about this classi- 

 fication, which constitutes systematic entomology, requires 

 a great deal of time and persistence on account of the great 

 numbers of species concerned. A good way to begin the 

 study of the kinds and classifications of insects is to make 

 a collection. Directions for this are given in Appendix II. 



