70 THE MONTHLY BULLETIN. 



Throughout the entire summer months broods upon broods, each 

 in turn producing other broods, give rise to millions of this destructive 

 pest, and this accounts for their great and infinite numbers. It 

 has been estimated that a single stem mother will give rise to one 

 billion insects during a single season. With the coming of cold weather, 

 and after the first frost, there is a rapid diminution in numbers, and 

 soon practically all of the winged individuals disappear. This is 

 brought about, especially in the case of the apple aphis, by the 

 devefopment of true sexual forms, male and female. 



Sexual Forms.— The parthenogenetic females of the late fall, instead 

 of producing individuals of their own kind, give birth to true sexual 

 forms, male and female, both of which are apterous. 



Sexual Female. — The egg-laying female is much smaller than the 

 summer form, and varies from a rich green to a brownish or reddish 

 color. The head, cornicles, feet and tips of antennie are dark. 



Sexual Male.— The males are very small, hardly half as large as 

 the other lice. They are easily recognized by their frail and slender 

 bodies, long legs and light yellowish color. The head and tail are 

 noticeably dark. They are much more active than are the sexual 

 females, with which they associate and may be confused. These sex 

 forms copulate and the female produces the eggs which give rise 

 to the first stem mother already referred to. "While -the life history 

 of this insect is typical in the number of generations, there are no 

 root forms, as in the cases of the woolly aphis and black peach aphis ; 

 neither do winged sexual forms appear as in the case of some other 

 species. 



Distribution. — Common throughout the entire State. A serious pest 

 in the central and northern parts. 



Food Plants. — The host plants of the apple aphis are not many. It 

 is found on the apple, pear, haw^thorn, quince and flowering crab. Of 

 the apples, those which appear to be the favorites are the Missouri 

 Pippin, Rome Beauty, Black Twig, Ben Davis, Greening, though it 

 works just as effectively on many other varieties. The Northern Spy 

 is fairly free from its attack. 



THE ROSY OR PURPLE APPLE APHIS. 



Aphis sorhi Kalt. 



{Aphis pyri Boyer. ) 



(Aphis malifoliw Fitch.) 



General Appearance. — This insect gets its common name from its 

 rosy or purplish color, which readily distinguishes it from the green 

 apple aphis. The head and thorax of the winged forms are dark. The 

 bodies of all are slightly covered with white powder which often gives 

 a grayish cast. 



