HABITS OF THE ADULT FLY 53 



it has been made after a long series of comparative 

 studies, and its truth will readily be admitted by any 

 one who has paid much attention to the flight of Dip- 

 tera. Cobb, in his paper on the Fungous Maladies of 

 the Sugar Cane, records a number of observations on 

 the flight of flies in connection with the distribution by 

 the flies of the spores of a fungous disease of sugar 

 cane. He states that he never succeeded in tiring his 

 flies very perceptibly if they had a free space to move 

 around in. When confined in a room they were kept 

 on the wing for hours without showing much fatigue. 

 By dissection he showed that with certain of the Sar- 

 cophagid flies the thoracic or wing muscles constituted 

 twenty-six and two-tenths per cent, of the weight of the 

 fly, and that the mass of the great thoracic muscles is 

 proportional to the apparent power of flight among dif- 

 ferent flies. He records also a remarkable example of 

 the power of flight of one of the larger flies. On a 

 voyage across the Mediterranean from Algiers to Mar- 

 seilles, he observed a Dipterous insect keeping pace with 

 the steamer "so accurately that it almost seemed as 

 if it were joined to the boat by some invisible rigid 

 connection. The boat left Algiers at noon and as long 

 as there was any light left by which to observe, the 

 insect kept its place steadily. This was in midsummer. 

 The insect never made any attempt to come aboard. 

 The boat was not particularly fast, her speed being 

 about thirteen knots." 



Every one who has driven a fast team of horses over 

 a road through pine timber must have noticed the ex- 



