1 82 The Control of Mosquitoes 



pass through the small openings into which the 

 larvae dart. When larvacide is appUed at the 

 edges of streams, mosquito larvas sometimes escape 

 beyond the treated zone and are immediately 

 snapped up by fish. When rainstorms remove the 

 algffi, debris, etc., and break up the hiding-places 

 in streams and ditches, the fish are most actively 

 employed and have a feast. In quiet waters 

 they pick up the larvae that venture far from their 

 hiding-places. 



In one instance two solid embankments were 

 placed across the Corundu River and extended 

 from Diablo Hill to Balboa. Between the embank- 

 ments was a large flat area of about five hundred 

 acres. During the rainy season much water col- 

 lected in it and was followed by a change in the 

 character of the vegetation. 



One of the growths was a moss-like weed that 

 had not been seen before. It grew in the water to 

 within an eighth of an inch or less of the surface 

 but did not quite reach it. There was enough 

 water above the growth to support Anopheles 

 larvas, but not sufificient for the fish to swim in. 

 This area was about a mile south of Corozal and 

 was not treated tmtil it had produced thousands 

 of full-grown larvae. This happened before the 

 flight of Isthmian Anopheles was tmderstood as it 



