READY FOR FLIGHT 115 



engaged from the wing-cases before they are fully 

 expanded and fit for flying. These genera quit 

 the pupa at the surface of the water, from which, 

 after resting upon it for a few moments, they take 

 flight. But this would evidently be impracticable, 

 and immersion in the fluid, and consequent death, 

 would result, were not the general rule in their case 

 deviated from.' 



