Why the fly

The chief advantage of Drosophila was one that historians have overlooked: it was an excellent organism for student projects. Drosophila kept an academic schedule. They were most plentiful in the autumn, when gardens and orchards were filled with rotting fruits and vegetables, and as they were accustomed to wintering over in human habitations, they happily bred year-round in the warmth of college labs. They were easily replaced and inexpensive to keep, thriving on anything that would support a growth of yeast (bananas quickly emerged as the ideal: not too juicy, cheap, and available year-round). If colonies were killed off by inexperienced or careless students, only a modest investment was lost. When cultures died out in the summer vacation, it was easy to start new cultures when student laborers returned in the fall. The craft skills of Drosophila were easily learned, and a fly colony could be easily maintained in the interstices of a busy undergraduate schedule. Animal colonies and greenhouse collections were far more exacting of time and skill and were too valuable to entrust to succeeding generations of green apprentices [34].

Kohler, Robert E. Lords of the Fly : Drosophila Genetics and the Experimental Life. University of Chicago Press, 1994. ISBN 0226450627.