PINK AND GREEN APHID OF POTATO. 207 



leave that food plant earlier in the season when out of doors. 

 In the insectary the eggs were placed indiscriminately on leaves 

 and stalks. These are pellucid green at first and later become 

 glistening brownish black. 



It is not known upon how great a range of food plants this 

 aphid will develop in the spring. In Maine it has never yet 

 been collected during this season upon anything but rose, which 

 would indicate that this is the favorite overwintering host plant 

 and the one ordinarily chosen for the deposition of the egg in 

 the fall. 



On October 9, 1908, great numbers of winged viviparous 

 females and winged males and wingless oviparous females were 

 found on Japanese rose bushes on the Maine Campus. They 

 were for the most part on the ventral surface of the leaves. The 

 winged viviparous females were presumably the fall migrants 

 and mothers of the true sexes. 



The stem mothers or females hatching from the overwinter- 

 ing eggs, were abundant upon these same bushes the next May 

 and by the thirteenth of the month were nearly mature and were 

 feeding at the half-opened leaf buds. On June 3 the progeny of 

 the first generation, or the stem mothers, consisted of mcture 

 alate and apterous viviparous females as well as immature aphids 

 of both the second and third generation. Usually by the first 

 of July only scattered colonies remain upon the rose and by 

 this time the summer generation may be found upon the potato. 



ECONOMIC SIGNIFICANCE. 



During certain summers enormous numbers of the pink and 

 green potato aphid have appeared over wide areas in Aroostook 

 County, the vines being attacked to an injurious extent in the 

 vicinity of Houlton and elsewhere. The colonies cluster thick 

 on stem, leaf and blossom stalk, blighting the stems and drying 

 the terminal leaves as is shown in figures 47 and 48. The time 

 of severest attack apparently varies somewhat, but the infes- 

 tation in Maine has not been excessive before early August 

 and is over with before the middle of September. Under con- 

 ditions favorable to aphid growth, an attack of less than two 

 weeks' duration suffices to kill the potato stalk for a distance of 

 4 to 6 inches from the tip, and the growth of the tubers on 

 plants thus weakened must necessarily be aflrected. Aside from 



