Natural Enemies 189 



screens. They invariably fly back and forth 

 in wind-shaded gullies containing brush, where 

 mosquitoes are more numerous than on the 

 adjacent higher land. In these sheltered places 

 when Culex were swarming about the observers 

 and biting them, the bats approached closely, 

 while when they were not being bitten by mosqui- 

 toes the bats were ftilly ten feet away. 



