TWO LEAFHOPPERS INJURIOUS TO APPLE NURSERY STOCK. 25 



Table XIV. — Length ofnymphal stages of the first brood of the rose leaf hopper on nursery 

 apple trees at West Chester, Pa., 1915. 



First brood, May and June. 



























Aver- 



























age 



























mean 



Date 

 of 























Total 



tem- 



First 



First 



Second 



Sec- 

 ond 



stage. 



Third 



Third 



Fourth 



Fourth 



Fifth 



Fifth 



nym- 

 phal 

 pe- 

 riod. 



pera- 

 ture 

 for 

 nym- 



hatch- 

 ing. 



molt. 



stage. 



molt. 



molt. 



stage. 



molt. 



stage. 



molt. 



stage. 



























phal 



























pe- 

 riod. 



1915. 



1915. 



Days. 



1915. 



Days. 



1915. 



Days. 



1915. 



Days. 



1915. 



Days. 



Days. 



°F. 



May 6 



May 11 



5 



May 14 



3 



May 21 



7 



May 28 



7 



June 7 



10 



32 



67.19 



May 7 



May 13 



6 



May 17 



4 



May 24 



7 



May 30 



6 



June 8 



9 



32 



67.33 



Do... 



May 14 



7 



May 21 



7 



May 29 



8 



June 4 



6 



June 12 



8 



36 



68.16 



Do... 



...do.... 



7 



May 22 



8 



May 28 



6 



June 2 



5 



June 10 



8 



34 



67.47 



Do... 



May 15 



8 



...do 



7 



...do 



6 



June 3 



6 



June 11 



8 



35 



67.79 



Do... 



May 12 



5 



May 20 



8 



May 26 



6 



...do 



8 



June 9 



6 



33 



67.44 



Do... 



May 16 



9 



May 23 



7 



May 29 



6 



June 5 



7 



June 12 



7 



36 



68.16 



Do... 



May 15 



8 



...do 



8 



May 30 



7 



June 4 



5 



June 11 



7 



35 



67.79 



May 8 



May 13 



5 



May 21 



8 



May 27 



6 



June 3 



7 



...do... 



8 



34 



67.70 



May 11 



May 16 



5 



...do 



5 



...do 



6 



...do 



7 



June 10 



7 



30 



67.85 



Do... 



May 17 



6 

 6.4 



May 22 



5 



May 28 



6 



...do 



6 



June 11 



8 



31 



68.29 



Average 



6.3 



6.4 



6.3 



7.8 



33.4 



67.74 











FIRST BROOD OF ADULTS. 



No attempt was made to obtain definite data on the longevity of 

 first-brood adults. Ninety adults, however, were confined in a Eiley 

 cage on a young apple tree on May 31, 1916, and the last leafhoppers 

 died on August 1 ; by this date many of the second-brood nymphs 

 had appeared. Thus, the length of life of the adults of this brood 

 is approximately two months. 



Second Generation. 



second brood of eggs. 



Length of incubation period. — An approximation of the length of 

 the egg stage of second-brood eggs (i. e., the summer eggs) is shown 

 in Table XV. The average length of the period was 25 days; the 

 maximum, 27 days; the minimum, 23 days. 



Table XV. — Length of incubation period of summer eggs deposited by first-brood females 

 of the rose leaf hopper, West Chester, Pa., 1916. 



Four pairs of adults placed in confinement on apple tree July 28, 1916, 4 p.m.; adults removed July 29, 4 p. m. 



Date of removal of newly 

 hatched nymphs. 



1916. 



Aug. 21 



Aug. 22 



Aug. 23 



Aug. 24 



Number 



of 

 nymphs 

 removed 



Incuba- 

 tion 

 period. 



Days. 



23-25 

 24-26 

 25-27 



Date of removal of newly 

 hatched nymphs. 



1916. 



Aug. 25 



Aug. 26 



Aug. 27 



Aug. 28 



Number 



of 

 nymphs 

 removed. 



Incuba- 

 tion 

 period. 



Days. 



