434 ENTOMOLOGICAL NEWS. [Dec., ’o8 
Pemphigus tessellata: Alternate Host, Migrants 
and True Sexes.* 
By Epira M. Patcu. 
(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 incana) from about 
April 20th 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, 
