yo LIFE-HISTORY STUDIES 



Since this work will go on through the greater portion of the 

 semester the student is expected to collect his specimens early 

 in the course and make observations from time to time to ascer- 

 tain developments. This can be done at the opening of each 

 laboratory period or oftener. 



For notes the same sized paper is to be used as for the exercises 

 requiring drawings. The exercise is to be given its regular 

 number and title. The date of collection should be indicated, 

 together with place and conditions. Each day observations are 

 made the date should be set down, together with memoranda 

 as to progress in life history, continuing thus until the organism 

 has matured or the term has closed. If the specimens die, more 

 should be collected. 



EXERCISE 39 



LIFE HISTORY OF THE COMMON HOUSEFLY 



A. The student will collect two or three dozen or more of 

 housefly eggs. These can be collected, either from neighboring 

 horse-manure piles, or adult flies may be captured and placed 

 in a breeding cage into which is put also a jar of horse-manure. 



B. Place the eggs into a jar which is partly filled with horse- 

 manure. The jar should be kept in a warm room. Cover the 

 jar with gauze or bobbinet. 



C. Observe the date on which the larvae hatch from the eggs. 

 You will now have the incubation period. 



D. Note the date on which feeding ceases and full growth has 

 been reached. You will now have the period of growth. 



E. After the larvae cease feeding they usually try to leave the 

 manure, crawling into drier portions or nearby debris and pre- 

 pare to pupate. This is called the prepupal period. 



F. Observe the date of pupation. 



G. After a given number of days in the pupal stage the fly 

 emerges; it is now an imago. If the fly is to live the student 



