LIFE HISTORY 19 



F., in twelve hours, but at 45° F. they did not hatch 

 until the third day, and then only when placed in a 

 warmer temperature for the purpose of studying them 

 under the microscope. 



Doctor Hewitt has carefully observed the hatching 

 of the eggs, and this is a process which has now be- 

 come familiar to many Americans through the excel- 

 lent moving-picture exhibitions given under the auspices 

 of the American Civic Association from films prepared 

 in England at the expense of Mr. Daniel Hatch, Jr., 



Fig. 5-— Egg of house fly; greatly enlarged. (Original.) 



Chairman of the Fly-fighting Committee of the Asso- 

 ciation. Doctor Hewitt's description follows : 



"A minute spHt appeared at the anterior end of the 

 dorsal side to the outside of one of the ribs [refer- 

 ring to two distinct curved rib-like thickenings along 

 the dorsal side of the egg] ; this split was continued 

 posteriorly and the larva crawled out, the walls of the 

 chorion [the eggshell] collapsing after its emergence. 



The Larva 

 We have just described how the egg hatches. The 

 young larva as it issues from the egg is a slender 



