222 INSECTS 
appear in the spring they should be destroyed wherever 
found, and the multiplication of the rest should be prevented 
by keeping the premises free from slop piles, barnyard 
manure, and other possible breeding places. In this way 
remarkable results have already been achieved, for in some 
communities, where the war has been waged persistently, 
they have been practically exterminated. If we consider 
the rate of increase, it is easy enough to understand why 
the flies are so numerous in the latter part of the summer. 
Starting with a single female fly on April 15, letting her lay 
120 eggs, and continuing the multiplication in this manner 
until fall, we may have eight generations, as follows: 
April 15 —1 
May 1 — 120 
May 28 — 7200 
June 20 — 432,000 
July 10 — 25,920,000 
July 29 — 1,555,200,000 
August 18 — 93,312,000,000 
September 10 — 5,558,720,000,000 
Total — 5,653,613,559,321 flies 
Of course we cannot expect every fly to reproduce in this 
way without fail, nor can we be sure that none shall be de- 
stroyed, as here assumed, but on the other hand we have 
given each female credit for only 120 eggs, while she may 
lay many hundreds in her lifetime. 
Ants have long been a favorite subject for the study of 
animal intelligence. They belong to the same order as bees 
and wasps, have the same remarkable powers of instinct, 
1F, L. Washburn, State Entomologist of Minnesota, gives a much higher 
estimate of the possible offspring of one fly in a season. His figures are 
214,557,844,320,000,000,000,000. See his circular No. 26, 1913. 
