BULLETIN 198. 



THE GRAPE LEAF-HOPPER. 



189 



the opposite side; for the purpose of holding the leaf firmly against 

 the cage, a piece of transparent gelatine was used, it being cut to cor- 

 respond with the pasteboard on the opposite surface. These were 

 held together on the leaf by means of ordinary paper clips. Strips 

 of fairly thick paper were glued on the upper side of the pasteboard, 

 leaving one edge free, under which an ordinary cover glass could 

 be pushed. These cover glasses could be readily changed and kept clean, 

 and the specimens could be easily examined, if necessary, with a com- 

 pound miscroscope. Only forty eggs were laid by two or three hoppers, 

 but these probably died prematurely. This number was laid in about 

 two weeks, which is a shorter period than most hoppers evidently live. 

 One laid ninety-six, two one hundred and ten, and one one hundred 

 and twenty-one. Since our observations in the field indicate that most 

 of the hoppers continue to lay eggs for one to two months, the number 

 of eggs laid will probably average from seventy-five to one hundred 

 and twenty-five. 



Rate of Egg Laying. In the case of three or four hoppers we were 

 able to follow pretty closely the rate at which the eggs were deposited, 

 and the total length of the oviposition period. The following tabulation 

 for one of these is given below. The totals are carried out for each date : 



Copulated June 23d. Case 51. 



Rate of Oviposition. 



"Total laid to July 17th. No further hatching record was kept for short intervals. 



Incubation Period. A large number of hoppers w r ere liberated on 

 our experimental vines at 9 A. M. May 29th, and removed at noon 

 2 BUL. 198 



