THE CANADIAN ENTOMOLOGIST, 51 



the times when the earliest butterflies were seen, when they became most 

 abundant, when the numbers perceptibly diminished, or specimens became 

 old and worn, and when the last were seen. It is particularly difficult to 

 decide upon the average age of individuals, when, as is not infrequently 

 the case, a brood of butterflies is augmented by gradual accretions for a 

 long period of time, three, four or five weeks. It is again difficult in the 

 case of those butterflies, and there are not a few of them, like some of our 

 Argynnidi, which appear upon the wing in mid-summer, receive a sudden 

 accession to their numbers a month or two after the advent of the earliest 

 and then only begin to lay their eggs. I, for one, can hardly believe 

 that all these earliest individuals perish before the season for egg laying, 

 and I even think from the condition of specimens, worse and worse as 

 the season progresses, that some of the earliest live to the last and are 

 upon the wing sometimes for two and three months of the year. 



ON SPECIFIC NAMES. 



BY A. R. GROTE, A. M., BREMEN, GERMANY. 



Dr. Williston, in his painstaking work on the Syrphidce, says : 

 " There are no generic and specific limitations in nature," and illustrates 

 the statement by the present knowledge of the family with which his 

 synopsis deals. And what Dr. Williston brings forward is- a mere quota 

 of the mass of evidence brought out by naturalists generally, and by ento- 

 mologists dealing with the different orders of insects. But while, theo- 

 retically, the essential unity of living forms or of nature as a whole may 

 be granted, the practical question of what names we shall bestow upon 

 our specimens and upon what basis these names shall repose, must be 

 solved. Our systems of nomenclature must be brought into consonance 

 with the facts observed. And it is well that our nomenclature be not too 

 rigorous, so that I have expressed the opinion in these pages that we shall 

 have to use in certain cases a trinomial title. With regard to the test for 

 genera in the moths, I have to refer for my conclusions to a paper in 

 Papilio, 3, 35, where I say that the amount and extent of the peculiarity 

 gives the criterion, not the kind. Every well-marked variation and modi- 

 fication of structure, which can be clearly made out by the microscope or 

 otherwise, is of generic value. The moment this rule is departed from, 

 we are thrown upon individual " opinions." All the characters which, 

 when well-marked, are of generic importance, are liable to slighter modi- 



