EXPERIMENT STATION REPORT. 



573 



with the season, and the development of the insects will be uniform. 

 By the middle of the month the Teras will be at work ovipositing, 

 and by the 25th larvae of both yellow and black-heads will be gener- 



tiioh water /e 



/ooifom of hoo 



Fig. 31. 



Sectional plan of a gaie for drawing water from bottom. Original. 



ally hatched. Eeflow May 1st if the season is normally advanced and 

 larvae are generally observed. It is a good plan to wait until half- 

 grown larvae appear, because then one is almost certain that no sound 

 eggs remain unhatched. 



