STATE HOETICULTUKAL SOCIETY. 93 



I have hitherto come up to the meetings of this Society — the 

 nearest a general scientific society we now have in Illinois — bringing 

 such contributions to knowledge from my field of labor as the year's 

 work had enabled me to make ; but this year I have come to ask 

 instead of give^ and the title which I have selected for this brief 

 paper is that of " Unsolved Problems in Horticultural Entomology." 

 Under this head I have gathered together a few entomological items 

 of practical importance concerning which we much need additional 

 information, and which, as it seems to me, you, as horticulturists, 

 can obtain almost without effort, for yourselves and each other ; 

 much more easily, certainly than any one can who does not come in 

 daily contact with with the trees and shrubs of the orchard, and 

 flowers, and plants of the garden. 



I first raise the question of the apple aphis. This is a minute, 

 sluggish, bluish green insect, six-legged, usually wingless, about the 

 size, when full grown, of the head of a small pin. It occurs in 

 great numbers on the under side of the leaves of the apple, especially 

 in early spring, causing the leaves to curl. It may be readily distin- 

 guished from any other insect with which it is liable to be con- 

 founded in that situation, by its sluggish movement, and by two 

 straight, projecting tubes near the hind end of the back. Beneath 

 the head is a stout, jointed beak, which it thrusts into the under 

 side of the leaf, sucking the sap, thus arresting the growth of the 

 cells of the under surface, while those of the upper surface continue 

 to grow. The leaf is thus stunted, and rolled, and curled, forming 

 a protective retreat for the insect colony. The presence of these 

 groups is often betrayed when it would not otherwise be noticed by the 

 occurrence of ants upon the leaves, these insects attending the plant 

 lice, as is the common habit of many of the species, for the purpose 

 of lapping up the sweetish exudation from their bodies. The mis- 

 chief done, especially to nursery stock, is often very great, and even 

 bearing trees may be so checked as to cause a failure of the crop. 

 The curled and stunted leaves contribute little to the life of the tree, 

 and as the injury occurs when the twigs should be making their 

 most vigorous growth, the result in the nursery may be the practi- 

 cal loss of the season, and the development of a gnarled and stunted 

 stock of little market value. 



Although this is a long known species, occurring in both Eu- 

 rope and America; its life history has never been fully made out, 

 neither has any really good method of preventing its injuries yet 

 been devised. Further, the missing facts in its biography are just 

 such as may quite possibly give us the means of controlling the rav- 

 ages of this species; and they are facts that can hardly be deter- 

 mined by experiment and purposed observation, but, as you will 

 presently see, will probably finally be stumbled upon by chance. 

 The greater the number of intelligent observers, consequently, who 

 will keep theii eyes open for these missing data the sooner will this 



