Entomology, 1883, whilst adding to the genus a new species, P. cycadis, remarks that he is “far from feeling sure that the genus will prove to be a natural one;” but he gives no reason for this opinion, and, in fact, reverses it by including a species in the genus. Mr. A. Morgan, in the Entom. Monthly Mag for October, 1888, follows the lead of Professor Comstock (as, indeed, he seems to do all through), and adds two reasons for doubting the generic position of Poliaspis: first, that it included only one species when first established, and, secondly, that the chief generic character regarded the abdominal features of the female, and not the shape of the scale or puparium. With reference to his first reason, it is evident that the discovery by Comstock of P. cycadis at once destroys it; and the mere fact that originally only one species was known does not in the least prevent the addition hereafter of any number of others. But, besides, it does not seem to me altogether satisfactorily established that, because, in three or four instances quoted by Mr. Morgan, Professor Comstock eliminated genera formed by Signoret, Targioni, &c., which genera only included single species, it must therefore be taken that this must be always agreed to. If it had been said that the formation of a genus, or even of a species, on a single specimen, is wrong, I should entirely agree. Moreover, I would advocate simplification as far as it can possibly be carried. But, when a large number of individuals are found occurring plentifully on certain plants, and year after year, and these individuals exhibit some organic character (not such trivial things as size, colour, and the like) not found in known genera, I conceive that an entomologist is justified in erecting them into a genus, even of only one species. I have never formed either a species or a genus without very careful examination of as many specimens (sometimes several scores) as I could get hold of; but, having established on single species such genera as Poliaspis, Lecanochiton, Inglisia, Cælostoma, I have had the satisfaction of finding my judgment confirmed by the discovery of other species clearly cognate. Of course, if, after the most careful study, an observer is to be made liable to the overthrow of his work on the ground that somebody else has not seen anything similar to that which he has observed, it will become very difficult to systematize in any branch of science. Mr. Morgan's second reason is of another class. He says that differences in the abdominal characters of Diaspid females ought not to “subserve generic purposes, as in that case the uniformity of the rule on which the genera of Diaspids have been established becomes imperfect.” I am not aware of any “rule” properly so called. Signoret, I observe, remarks that differences in the forms of the puparia may be con-