OYSTER-SHELL BAEK-LOTTSE. 4:5 



nomena in the case would be satisfactorily explained by the theory 

 that the female Bark-loase, in these instances, had failed to become 

 mpregnated. 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, alter 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 Asjnd'nAns 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 Coccidce, 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 middle, and a new genus, named Ifi/tilaxjm, (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. < 



