th 
Intinors NatrurAL History SurvEY BULLETIN Vol. 26, Art. 1 
stroying piles and other wood structures; mayflies have caused damage in certain local 
t . J 
the other, occurring in the Belgian Congo, areas. Unusual hordes of these insects 
bores into freshwater sponges. may leave the water on the first suitable day 
Occasionally, over a period of years, adult after adverse weather conditions, or other 
PHOTOGRAPH FROM WORLD WIDE PHOTOS. 
Fig. 1.—The picture above was published in the Chicago Daily News on July 8, 1946. It 
carried the legend: “May flies stop motorists. Lawrence Rutz stops his truck on the west channel 
bridge at La Crosse, Wis., yesterday to clear May flies from the front of the vehicle. The 
insects got so thick they obstructed the view of the driver, clogged radiators and made roadway 
of the bridge slippery.” 
