TWO LEAFHOPPERS INJURIOUS TO APPLE NURSERY STOCK. 7 



field observations it was found that this species hibernates in the 

 adult stage in woodlands near the nursery at West Chester. The 

 adults become active in the spring about a week earlier than mail, 

 confining their feeding at first to the foliage of skunk cabbage. 

 From this plant they scatter to grasses and weeds beneath the apple 

 trees in the nursery a few days prior to the first appearance of mali. 

 During the early spring they prefer to feed on any low green vegeta- 

 tion in the nursery row, and never become abundant on the foliage 

 of apple until about mid-season. At this time they appear in num- 

 bers associated with mali on the terminal leaves. The extent of 

 damage caused by birdii is small compared with that caused by 

 the common apple leafhopper, and for this reason little attention 

 has been paid to it heretofore. 



Fhvescens differs from birdii by the absence of the characteristic 

 white markings of the pronotum and the smoky bands crossing the 

 elytra. 



This species is allied very closely to birdii in appearance, and proba- 

 bly in habits and life history, but it is less abundant on the apple. 



Unicolor is readily separated from mali by the absence of the 

 conspicuous white markings of the face and the notum, by its greater 

 length and robustness, and by the presence of a pale white spot on 

 the middle of the anterior margin of the pronotum and a blue blotch 

 on the scutellum. 



Few field observersations were obtained in regard to the habits of 

 unicolor. The nymphs of the first brood were found on apple at 

 approximately the same date and about as abundantly as those of 

 mali at Hagerstown, Md. The adults of this species do not confine 

 their attack to the terminal leaves, being found more frequently on 

 the lower part of the trees. This species was taken in scant numbers 

 on apple in the vicinity of West Chester and the injury caused by 

 it was negligible. 



LIFE HISTORY AND HABITS. 



Methods of Study. 



In studying the life history of the two species of apple leaf hoppers 

 concerned in this bulletin all data were obtained under outdoor 

 conditions by rearing the insects on young apple stock in the nursery 

 row. Seedlings were planted out early in the spring of 1915 and 

 again in 1916 on a plot of ground at one end of a few nursery rows. 



Riley cages and arc-light globe cages (PI. II, A) were used for 

 obtaining records of the length of the egg stage, the extent of repro- 

 duction per female, and the longevity of adults of the different 

 broods. The globe cages were well shaded from the sun by means 

 of large muslin covers over their tops, while ventilation was obtained 

 both from above and below. With the use of such cages practi- 

 cally normal conditions were secured for the rearing of the leafhopper 



