THE LIFE HISTORY OF TWO SPECIES OF PLANT-LICE, 
INHABITING BOTH THE WITCH-HAZEL AND BIRCH. 
INTRODUCTION. 
The study of the life history of the Aphidide or plant-lice, in con- 
nection with their peculiar and frequently destructive habits as well 
as the remarkable traits of many of the species, has offered a most 
fascinating field for research and study to many naturalists, and their 
labors have brought to light numerous interesting facts regarding the 
habits and economy of various species. Much is still to be learned 
concerning the annual migrations and the intermediate habits and 
changes of the majority of our Pemphigini, the architects of galls or 
excrescences on the leaves and other portions of certain trees and 
shrubs, which they desert, at the opportune time, to vanish com- 
pletely from sight. These migrations and sudden disappearances of 
the gall-inakers leave the observer in doubt as to the whereabouts of 
the connecting links of the fleeting migrants, of which very few have 
thus far been discovered. During autumn and early winter the 
return migrants make their appearance, as suddenly and mysteriously 
as the spring migrants disappear, without bearing a clue as to their 
former habitations. This is for the purpose of restocking their origi- 
nal host plants with their eggs, to enable the species to commence a 
new cycle of existence the following spring. 
Interesting as the life history of all these insects is, there are few 
or none among them which have a more remarkable or a more diver- 
sified cycle of existence than two species belonging to the genera Hor- 
maphis and Hamamelistes, both of which, alternately, inhabit the 
witch-hazel, Hamamelis virginica, and the birch, Betula nigra. The 
study of the life history of these, after numerous failures and disap- 
pointments, covering a space of nearly twenty-two years of patient 
labor, the writer has been fortunate to bring to a successful conclusion. 
The drawings were all made by Miss L. Sullivan under the writer’s 
supervision. 
HORMAPHIS HAMAMELIDIS Fitch. 
The synonymy of the oldest of the two species, as it will now 
stand, is: 
Hormaphis hamamelidis Fitch. 
Byrsocrypta hamamelidis Fitch, N. Y. Cat. of Hom. Insects, 1851, p. 69. 
Hormaphis hamamelidis Osten Sacken, Stett. Ent. Zeitung, 1861, p. 422. 
Hormaphis hamamelidis Walsh, Proc. Ent. Soc. Philad., VI, 1866-67, p. 281. 
Hamamelistes cornu Shimer, Trans. Am. Ent. Soc., I, 1867, p. 283. 
Hormaphis hamamelidis Thomas, Trans. Ill. State Hort. Soc., 1876-77, p. 
199: 
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