156 TRANSACTIONS OF THE ILLINOIS 



to hatch, which are destroyed by the following cold period ; their insect 

 enemies, which prey upon them, are very numerous; even the tiny eggs 

 are not overlooked by their ravenous foes. 



It is maintained by some orchardists, and I presume they are correct, 

 that some varieties are much more liable to the attack of this species than 

 others. What species have suffered most in Illinois I am unable to say ; 

 the Northern Spy and Red Astrachan are said to be among the least liable 

 to be affected. 



As is common with other species, the colonies will be found com- 

 posed of individuals of all ages, mingling and feeding together. 



The newly-born are at first nearly white, but soon begin to change 

 to a pale, dull, greenish yellow, gradually assuming the color of the adult, 

 as heretofore given. As the leaves unfold, they gather on the under sur- 

 face and upon the leaf stalk, and by pumping out the sap and thus check- 

 the growth of the under surface, Hhile the upper surface continues to grow 

 and expand, the leaf necessarily curves backwards, often to such an extent 

 that the apex touches the stalk. This forms a shelter for them by which 

 they are shielded from the rays of the sun. This species-has occasionally 

 been very abundant in Illinois and Missouri. 



Re7nedies. — I will defer the account of the remedies and parasites 

 until I have concluded the descriptions of the species, for the reason that 

 the remedy for one species is generally equally applicable to another, and 

 therefore it is unnecessary to mention them more than once. 



14. Aphis malifolicB, Fitch. The Apple-leaf Plant-louse. 



This species, which was first described by Dr. Fitch in 1856, has, very 

 probably, been often mistaken for the preceding, on account of its simi- 

 larity in habits. In fact, Walker, in the appendix to his catalogue, gives 

 this name as a mere synonym of the former. It is possible it is but a 

 variety of the former ; but I here follow Dr. Fitch, and give it as a distinct 

 species. 



It is larger in size than the A. mali, measuring rather over one-seventh 

 of an inch to the tips of the closed wings ; of a shining black color 

 throughout ; the legs are also entirely black, an occasional specimen being 

 found in which these are pale or brownish at the base. The wings differ 

 very distinctly from those of the preceding species. They are more 

 slender, and the fourth vein (of the front wings) is relatively shorter and 

 more strongly curved throughout its entire length. In consequence of 

 this curvature, it is nearer the second fork at its base than at its tip. 

 The third vein is but slightly abortive at its base ; the second and tliird 

 veins are parallel with each other, though they are sometimes nearer each 

 other at the tip than at the base. In the former species, the first fork 

 branches from the third vein beyond its middle ; in this species, it is 

 given off much nearer the base, at about one-third the distance from the 

 base to the tip; in the former species, the second branch or fork is much 

 less than half as long as the first ; in this species, it is usually half as long. 



Dr. Fitch, from whose report the above description is chiefly taken, 

 states that he gathered this species from the leaves of the apple trees in 



