CHAPTER V. 

 CRUSTACEA. 



STUDY OF THE LIVE CRAYFISH. 

 FIELD STUDY. 



Where to find Crayfishes. Look under stones in shallow 

 creeks, under ledges of rock, or overhanging banks of streams. 

 Remember that crayfishes are nocturnal and are usually hiding 

 during the daytime. Note all the kinds of places in which you 

 find them, and where they are most numerous. Are they in deep 

 or shallow water? In clear water or muddy? In fresh water or 

 foul ? In quiet water or in rapid currents ? Over mud, or gravel, 

 or sand ? 



How they Escape. In turning over stones or tin cans in a 

 stream, note closely how the crayfish escapes. Which end goes 

 foremost? What is the chief organ of locomotion? How is this 

 used? How far does a frightened crayfish ordinarily go before 

 stopping, if not closely pursued ? Does it stir up mud in its 

 flight? If so, how is this done? Does the stirring up of mud 

 benefit the crayfish? If the crayfish goes some distance, is the 

 rate of motion uniform? Explain. 



Color of the Crayfish. Note the color of the crayfish in rela- 

 tion to its surroundings, especially the color of the bottom over 

 which it passes. Is its color an advantageous one ? What if it 

 had the color of a boiled crayfish? Are all crayfishes of the same 

 color? How account for the difference? 



Crayfish Holes. Where are these most abundant? Do they 

 all have "chimneys "? Is the chimney of the same color as the 

 surface soil? How high are the chimneys? Are 



33 OF THE 



UNIVERSITY 



F 



