14 



BULLETIN 805, IT. S. DEPARTMENT OF AGRICULTURE. 



deposited per female in cage 1 was approximately 24; in cage 2 

 approximately 22. (See Table VI.) 



Table VI. — Number of second-brood nymphs produced by first-brood adult apple leaf- 

 hoppers in confinement, West Chester, Pa., 1915. 



CAGE No. 1.— TWO PAIRS OF FIRST-BROOD ADULTS PLACED IN CAGE ON YOUNG 

 APPLE TREE JUNE 30, 1915. 



Date of examination. 



July 13 

 July 17 

 July 20 

 July 22 

 July 24 



Number 

 of second- 

 brood 



nymphs 

 removed. 



Date of examination. 



July 27 



July 30 



Aug. 10 



Average 



Number 

 of second- 

 brood 

 nymphs 

 removed. 



24 



Cage No. 2.— THREE PAIRS OF FIRST-BROOD ADULTS PLACED IN CAGE ON YOUNG 

 APPLE TREE JUNE 30, 1915. 



July 14 

 July 17 

 July 20 

 July 22 

 July 24 

 July 27 



July 29 



July 30 



Aug. 10 



Average 



22 



Second Generation. 



SECOND BROOD OP EGGS. 



Length of incubation period. — As will be noted in Table VII, the 

 length of the egg stage of this brood is somewhat shorter than that 

 of the first brood. This fact undoubtedly is due to the higher tem- 

 peratures occurring throughout the incubation period of the second- 

 brood eggs. As in Table III only an approximation of the length of 

 the incubation period was obtained. The average incubation period 

 of second-brood eggs was 6 to 8 days; the maximum, 9 to 11 days; 

 the minimum, 3 to 5 days. 



Table VII. — Length of incubation period of second-brood eggs of the apple leafhopper, 



West Chester, Pa., 1915. 



TWENTY-FIVE PAIRS OF FIRST-BROOD ADULTS PLACED ON APPLE TREE JULY 7, 

 1915, 3 P. M.; ADULTS REMOVED JULY 8, 3 P. M. 



Date of removal of newly hatched nymphs. 



July 12, 3p.m. 

 July 13,3 p.m. 

 July 14, 3 p. m. 

 July 15, 3 p. m. 

 July 16, 3 p.m. 

 July 17, 3p.m. 

 July 18, 3 p. m. 



Average . 



1915. 



Number 



of 

 nymphs 

 removed. 



Length 

 of incu- 

 bation 

 period. 



Days. 



3- 5 



4- 6 



5- 7 



6- 8 



7- 9 

 8-10 

 9-11 



6- 8 



Average 

 tempera- 

 ture for 

 entire 

 period. 



°F. 



77.08 

 77.42 

 77.50 

 77.66 

 78.05 

 78.86 

 79.54 



78.01 



