10 Transactions. — Zoology. 



Entomology, 1S83, whilst adding to the genus a new species, 

 P. cy cadis, 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, ISSS, follows the lead of Professor Comstock (as, 

 indeed, he seems to do all through), and adds two reasons for 

 doubting the generic position of PoJiaspis : first, that it in- 

 cluded only one species when first established, and, secondly, 

 that the chief generic character regarded the abdominal fea- 

 tures 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 estabHshed that, because, in three 

 or four instances quoted by Mr. Morgan, Professor Comstock 

 elim in ated 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 

 occtirring 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 estabhshed on single 

 species such genera as PoJiaspis, Lecanochiton, Inglisia, 

 Ccehstoma, I have had the satisfaction of finding my judg- 

 ment 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 estabhshed 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- 



