2 BULLETIN 90, U. S. DEPARTMENT OF AGRICULTURE. 



this insect had become quite common, and many of the buds were 

 covered with the females and young. Examination of surrounding 

 localities disclosed the same conditions of infestation. The aphides 

 increased rapidly until the cold weather in December checked, 

 although it did not entirely stop, their reproduction and growth. In 

 January, warmer weather again prevailing, the rosebushes began to 

 grow rapidly, and the rose aphis became very abundant on the tender 

 stems and buds. It continued abundant and developed rapidly dur- 

 ing the months of February and March, although syrphus-fly larvae 

 devoured thousands. Early in April, however, there occurred sev- 

 eral very warm days when the temperature rose to 100° or 101° F., 

 and immediately the numbers of aphides were greatly reduced. 

 Afterwards the aphis occurred scatteringly on the roses and caused 

 very little damage. This was due in part to extreme heat and the 

 work of parasitic and predaceous enemies, and to the fact that in 

 June the roses became more or less dormant and ceased active 

 growth for some weeks. By the middle of August the rosebushes 

 had resumed active growth, and this insect again began to increase 

 rapidly and to cause damage, continuing to multiply and injure the 

 roses until October 1, 1910, when observations ceased. 



At Washington, D. C, during October and November, 1912, this 

 aphis was very abundant and injurious to roses grown in the yards 

 and gardens of the city. But by November 29 only a few aphides 

 remained on the plants, although these persisted as late as Decem- 

 ber 16. 



DESCRIPTION. 1 



The rose aphis occurs in two forms, one in which the body is of a 

 pinkish color and the other in which the pink is replaced by bright 

 green. Both forms may be present on the same bush or twig, and in 

 some cases all on one bush may be green and all on another near it 

 pink. It would appear from the writer's observations that the green 

 aphides are much more abundant during the cooler months than the 

 pink forms. 



The winged female (fig. 1, a) has a pear-shaped body which in one 

 form is pinkish and in the other bright green. The thorax is largely 

 black, apparently deeper black in the green form, and there is a row 

 of black spots on either side of the abdomen. These colors may vary 

 slightly in shade. The antennae, cornicles, ends of femora, and the 

 tarsi are black, while the other parts of the legs are whitish. In both 

 pink and green forms, however, the head may be entirely black, and 

 the black antennae and cornicles may be hyaline at the tips. The 



1 Another aphis commonly found on the ros6 is known as the small green rose aphis {Myzus rosanim 

 Walk.), but this can be distinguished by its smaller size and by the fact that it has only a green form. 

 This species i:; shown in figure 2, in both winged state (a) and wingless state (6) with many dotails of struc- 

 ture. This aphis will yield to the same treatments as the common rose aphis. 



