56 
FIRST ANNUAL REPORT OF THE 
from the general surface of their bodies, and both are “ Plant-lice,” inasmuch as they 
both belong to the Aphis family ; but they differ in their native country, they differ in 
the structure of their wing-veins and consequently in the genus to which they are 
referable, and they differ very widely in their habits. 
The true “Woolly Plant-louse ” is an imported insect, having been in reality intro' 
duced into America from Europe ; though, singularly enough, it was misnamed in 
England “ the American Blight,” when it was first noticed in that country towards the 
close of the last century, and was erroneously supposed to have been introduced there 
from America. It is now, however, pretty clearly ascertained to have existed on the 
continent of Europe for time immemorial, and it probably emigrated thence into 
England on imported apple-trees.* The Apple-root Plant-louse, on the contrary, is a 
native American species, and in all probability infested our wild Crabs and Thorns in 
the olden time, and, when apple-trees were introduced here, saw fit to attack them also. 
In the typical or normal Plant-louse there are in the front wing three branch-veins, 
springing successively out of the main or rib-vein which coasts along the outer or anterior 
edge of the front wing. In the genus to which the Apple-root Plant-louse belongs 
{Pemphigus), the 3rd of these branch-veins is perfectly simple ; in the genus to which the 
true “ Woolly Plant-louse ” belongs ( Eriosoma , otherwise known as Schizoneura or 
Myzoxylus), the 3d of these branch-veins is once-forked; in the genus to which the 
common Apple-tree Plant-louse belongs (Aphis,) the 3d of these branch-veins is twice- 
forked. Thus, on the very same Apple-tree, may be found examples of all these three 
genera — namely, the Apple-root Plant-louse, the true Woolly Plant-louse and the 
common Apple-tree Plantffouse — all distinct from each other by a very obvious 
character, and only in very rare and exceptional individuals of any of them running 
together by intermediate grades. 
Harris indeed, on the authority of Hausmann and Knapp, asserts that the true 
“ Woolly Plant-louse ” never has any wings at all.t But Amyot and Serville describe 
the male as winged, (Hemipt. p. 612); Westwood describes both sexes as winged, though 
he confounds the genera ( Pemphigus and Eriosoma) together, ( Introd . II. p. 440 and 
Synops. p. 118); and lastly Mr. A. E. Verrill discovered in Connecticut in October 
numerous winged specimens, both of the males and of the females. (. Practical Entomol¬ 
ogist, I. p. 21.) 
The true “ Woolly Plant-louse ” is a northern species, and, according to the European 
entomologist, Blot, cannot stand a hot climate even in its native country, Europe, 
being confined to Belgium, the north of France, Germany and England. Hence, so 
far, it has occurred in this country almost exclusively in New England. The. Apple- 
root Plant-louse, on the other hand, seems to be far more destructive in a hot southern 
climate than it is towards the north. Again: the true “Woolly Plant-louse” 
never burrows underground to get at the roots, but inhabits exclusively the 
trunk and limbs of the Apple-tree, where it secretes large masses of cottony down. 
The Apple-root Plant-louse, on the contrary, lives habitually undergound, sucking the 
sap from the roots and causing thereon large excrescences and swellings, among which 
it secretes a bluish-white downy substance, which, at first sight, has much the appear¬ 
ance of mouldiness. It is, doubtless, true that, according to Dr. E. S. Hull, of Alton, 
* See Harris’s Injurious Insects, p. 242, and Amyot and Serville’s Hemiptera, p. 606. 
f See Harris’s Injurious Insects, p. 243. 
