Chap. 5 



ANIMALS AND THEIR ENVIRONMENTS 



69 



Fig. 5.2. Diagram showing the approximate number of living species of animals. 

 The grand total is often given as one million. Numbers differ greatly with the 

 methods and time of counts. New species of insects are being discovered even in 

 familiar places; probably only a fraction of all the tropical insects have been de- 

 scribed. (Courtesy, Hunter and Hunter: College Zoology. Philadelphia, W. B. 

 Saunders Co., 1949.) 



for support. Giant grasshoppers are small compared to the largest lobsters, 

 their marine relatives. Blue whales, the largest living animals, are ten times as 

 long as elephants, more than twenty-five times heavier, and, like large ships, 

 are helpless when stranded (Fig. 5.4), 



Only the smallest mammals burrow or live in grassy runways. The pigmy 

 shrews are very small, one of them, Microsorex hoyi winnemana, total length 

 with tail, 3.12 inches, is the smallest mammal known in North America. Noc- 

 turnal and mouse-like but more slender it travels comfortably in a runway 

 half an inch wide. 



