The Necessity of Water for Flies 



W. C. COKER. 



University of N. C, Chapel Hill, N. C. 



In the January number of the Review Mr. J. S. Lozier makes 

 an interesting observation on the necessity of water to the life 

 of flies. When I read his statement that if no possible source of 

 water were left in the school-house when it was closed on Friday 

 that all the flies in the building would be dead by Monday, I was 

 so surprised that I decided to make a checked experiment to test 

 the need of flies for water. Four tumblers were fitted with 

 covers allowing the entrance of air and in two of them were 

 placed several pieces of soaked Sphagnum moss. The other two 

 were left empty. Two flies were put into each of the tumblers 

 except one of those with Sphagnum — which got only a single fly. 

 On examination after twenty-four hours the four flies in the two 

 empty tumblers showed a distinct loss of enthusiasm — the other 

 three were as lively as ever. After forty-six hours one fly was 

 dead in each of the empty tumblers and their two prison mates 

 were very weak — one of these died within the next two hours, but 

 the fourth, not being quite gone I decided to try to revive it. A bit 

 of soaked Sphagnum was placed at its head and it drank greedily 

 and long. After a few minutes it had shown a gratifying degree 

 of convalescence, recovering sufficiently to walk actively about 

 and even taking a flight. The three flies in the tumblers with 

 Sphagnum were still active, but slower in their movements than 

 at first. 



Wet moss was left with the revived fly, but at the end of 

 the third day (72 hours) it was dead, as were also two of the three 

 flies in the two other water-containing tumblers. The only fly 

 now alive was too weak to walk, but when a sweet boiled prune 

 was placed at its head it sucked in the syrupy liquid and within 

 ten minutes was making flights in the tumbler. 



This experiment shows that house flies cannot do without 

 water for more than 48 hours or without food for more than 72 

 hours at the temperature under which the test was made, which 

 was about 70 degrees F. 



About two weeks later when the temperature was unusually 

 high (85 to 90°) the experiment was repeated, four flies being 

 put in each of four tumblers — two tumblers with and two with- 

 out water. In this case all the flies without water died within 

 twenty-four hours and most of them within fourteen hours. Most 



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