8 BULLETIN" 774, TJ. S. DEPARTMENT OF AGRICULTURE. 



In 1916 infested prune leaves began to curl at the beginning of 

 April, such leaves having one or more colonies of adult stem mothers 

 and first-instar young. As April progressed the leaf-curl became 

 more and more pronounced and the colonies increased rapidly. 



About the middle of the month the most heavily infested leaves 

 began to have a j^ellowish appearance in the form of blotched areas 

 at the points where the aphids were most abundantly settled. On 

 April 21 a few leaves were found to have their under surfaces quite 

 covered with feeding aphids, and at the end of the month such leaves 

 were abundant, while twigs and limbs were covered with a sticky 

 "honeydew," and here and there young fruits were coated with this 

 substance. During May and June this condition was greatly aggra- 

 vated in the orchards examined. 



The spring winged form first appeared April 21, and throughout 

 May and June increased in numbers, and after the middle of May 

 there was a corresponding decrease in the numbers of wingless adults 

 produced. By July 1 the mature wingless individuals had dimin- 

 ished greatly in quantity and thereafter their numbers dwindled so 

 that by the middle of August none were to be found. In no instance 

 in 1916 was an infestation prolonged beyond this date, but in 1914 

 in the same locality a small but vigorous infestation occurred through- 

 out September, later becoming annihilated by natural enemies. 



In the rearing cages it was found that the transfer of newly born 

 young was very frequently attended by the loss of the insect, and 

 in most cases the adult was transferred when it was desired to make 

 observations on a new plant. Several transfers of larvae and adult 

 wingless individuals from plum to apricot failed, while others re- 

 sulted successfully. Infested apricot leaves did not curl as badly 

 as those of prune and plum. 



THE SPRING MIGRANT. 



Description. 



In the first three instars the nymphs of the migrants do not differ from those 

 of the wingless spring form, except that the third-instar individuals are some- 

 what narrower. 



Pupa. — Light green; eyes dark red; tarsi and apex of beak dark gray. On 

 the body ground color is superimposed a narrow dorsomedian stripe of darker 

 green. Thorax broadened to twice the width of the prothorax. Wing pads 

 yellowish white. Body with pruinose covering as in wingless nymph. 



Adult. — Light green; eyes red; antennas light gray, basal portion of third 

 joint hyaline yellow; head, thoracic lobes, and sternum dark grayish black; 

 scutellum yellowish brown; prothorax, sides of thorax, and wing insertions 

 greenish yellow ; wings hyaline, stigma and veins gray ; legs pale greenish yellow, 

 apices of tibiae and the tarsi dusky gray; abdomen and style pale green or 

 greenish yellow ; cornicles pale at base, dusky at apex. Beak pale, extreme tip 

 dusky. 



Form elongate, the abdomen with parallel sides. 



The dorsum and sides are covered with white pruinose " meal," on the ab- 

 domen the " meal " occurring in transverse bars. 



