45 
[ 305 ] 
nomena in the case would be satisfactorily explained by the theory 
that the female Bark-louse, in these instances, had failed to become 
impregnated. In this case she might perish without forming 
eggs, or she might go on to the formation and deposition of her 
ova, since we may infer from analogy, such for example as that 
of the common fowl, that the presence of the male is not essential 
to the formation of ova, but only to their fertilization. This theory 
is so plausible that 1 can scarcely avoid the conclusion that it af¬ 
fords the true explanation of a part, at least, of these cases; but 
how large a proportion, if any, is of course wholly a matter of 
conjecture. 
The absence of the Chalcis of the Bark-louse in this locality 
will furnish an excellent opportunity for testing the practicability 
of transporting it thither from those places where it is known to 
exist. If, after taking the necessary preliminary steps, as described 
in a former part of this article, we should find, next September, 
upon the trees experimented with, the characteristic holes in the 
scales which mark the exit of the Chalcis, we should know that 
the friendly parasite had entered upon its work. If such an ex¬ 
periment could be conducted to a successful issue, it would fur¬ 
nish one of the most admirable instances on record of the triumph 
of science, in its application to economic entomology. 
NOTE UPON THE CLASSIFICATION «OF THIS SPECIES. 
"We have in the more Northern sections of the United States, two species of Bark- 
louse infesting the apple tree: one a native American species, known as Harris’s Bark- 
louse, which prevails mostly South of the thirty-ninth parallel of latitude, though found 
in diminishing numbers considerably farther North; the other, supposed to be an im¬ 
ported species, much more injurious than the other, and occupying a more Northern 
geographical range, often called, by way of emphasis and as indicative of its notorious 
character, simply the Apple-tree Bark-louse, or more specifically, the Oyster-shell Bark- 
louse, this name being derived from the shape of the scale. It is the latter species of 
which we have here been treating. 
This species has been classed by all our more recent entomological writers, under the 
genus Aspidiotus of Bouche, following the determination of Dr. Fitch, as obtained from 
Mr. John Curtis, a distinguished English entomologist. In the recent elaborate re¬ 
vision of the family of Coccidse, by a French author, M. Signoret, the genus Aspidiotus 
is restricted to those species having a rounded form, with the larva scales attached at or 
near the middie, and a new genus, named Mytilaspis , (meaning muscle-shaped shield,) 
is formed to contain those species which have a long narrow form, usually a little curved 
to one side, like the shell of a muscle, and having the larval scales attached to the ante¬ 
rior and smaller extremity. 
