24 STATE HORTICULTURAL SOCIETY. 



females are developed. In the station laboratory breeding cages 

 these winged forms first appeared on the 26th of August. Some 

 of the winged forms leave the infested tree and fly to other trees, 

 where they establish another colony by bringing forth living young. 

 Late in the fall, toward the approach of cold weather, some of the 

 agamic females bring forth living, wingless and mouthless true males 

 and females. These pair and the females each develop a single fertilized 

 egg and perish. 



Each aphis, whether winged or wingless, is independent, and de- 

 rives its nourishment by piercing the bark with its long beak or mouth- 

 parts and sucking the sap below. 



In the northern part of Missouri most of the woolyaphis perish 

 during the severe cold of winter, and the eggs are frequently the only 

 means of continuing the species the following summer. In the south- 

 ern half of the State, however, the aphids themselves are usually able 

 to hibernate in large numbers, and hence it is that we find this pest so 

 much more numerous in that section. One may easily verify this 

 statement by examining the lower roots, near the base of the infested 

 tree, during the winter. I have seen hundreds of them alive and active 

 in such places every month in the year; but they appear to feed very 

 little, if at all, during the winter, beginning to feed at the first approach 

 of warm weather in the spring. Each hibernating aphis commences 

 to bring forth living apterous, agamic females just as soon as warm 

 weather is established ; and as hundreds of them may hibernate on the 

 roots of a single tree, it is readily understood why this insect is so 

 numerous in South Missouri. 



But in order to determine whether or not the limb form would 

 spread to and infest the roots, some wooly-aphis from the limb of an 

 infected tree in Jackson county were obtained and introduced June 

 28, on the limbs of the young apple trees in the other two root cages* 

 The trees contained no insects except those placed on the limbs. The 

 root-cages were isolated in large breeding cages in the green-house. 

 In the course of a week the aphids had established flourishing colo- 

 nies on the branches, and at the expiration of a month they had spread 

 down the trunk' in scattered and isolated places, and in one case had 

 attacked the roots near the trunk. In two weeks more the roots of 

 all the trees had several well-established colonies upon them. 



From these observations and facts it is believed that what little of 

 the aerial or limb form of the apple tree wooly-aphis we have in this 

 State is now derived from the root form. Of course, it will be under- 

 stood that I do not imply by this statement that ihe original form of this 

 aphis was root inhabiting, for I am decidedly of the contrary opinion. 



