484 ENTOMOLOGICAL NEWS. [Dec., 'o8 



Pemphigus tessellata : Alternate Host, Migrants 

 and True Sexes.* 



BY EDITH M. PATCH. 



(Plate XXIV) 



Ever since Fitch recorded in his brief, original description in 

 1851 "I have searched in vain for winged individuals of this 

 species," the alder blight has been from time to time an object 

 of speculative interest to aphid observers, although if any real 

 attempt has been made to trace the flight of the migrants and 

 locate the winter eggs' it has been heretofore unrecorded. 



With a species so conspicuous and of such wide distribution, 

 the absence of a knowledge of its different stages for the half 

 century or more since it was described would seem strange were 

 it not that the species certainly gives as defiant a dare to the life 

 history detective as a Pemphigus can and that is saying a good 

 deal. 



To begin with there seems to be no place in the apparently 

 closed cycle of alder blight for an alternate host and winter 

 eggs. According to the observations of the writer for the past 

 five years, apterous viviparous forms of Pemphigus tessellata 

 are present on the alder branches (Alnus woma) from about 

 April 2Oth to late October, weather permitting, and the rest of 

 the year hibernating as young apterous viviparous forms in 

 clusters or singly among the fallen leaves at the base of the 

 alder. The return of these hibernating young to the alder 

 branches in the spring completes an apparent cycle for a single 

 host plant and certainly suggests no need for variety in diet. 

 It was not then with any thought of an alternate host that these 

 observations were begun for this species in Maine but with the 

 hope of finding at some time during the year a sexual gener- 

 ation upon the alder. Protected under the flocculent mass 

 secreted by this Pemphigus the presence of a winged gener- 

 ation is not revealed (unless special collection and search for 

 forms with wing pads is made) until the form is mature. From 

 late August until the middle of September at the same time the 



* Papers from the Maine Agricultural Experiment Station: Ento- 

 mology, 30. 



