111)0 THE BUTTERFLIES OF NEW ENGLAND. 



a circular of inquiry I addressed to many persons, it lias of course been impos- 

 sible to weigh the evidence for exactly what it was worth. Some of it, as was 

 to lie expected, had to be thrown out altogether as coming from those who 

 were not sufficiently observant to have distinguished between the new pest and 

 its allies, also destructive to cabbages. To adopt indiscriminately all the 

 data offered would ha\c led to a chaotic result ; we should have been obliged, 

 for instance, to say that the butterfly appeared in Ohio in 18(55, when it 

 had only that year crossed the northern border of New England ; or that 

 it reached central Illinois in 1871 or 1872, or even in 185H, when it had 

 not yet been borne across the ocean ; or tliat it appeared in Georgia in 

 1862 and was abundant there in ISfili, some ten years before its time. 

 More possibly correct is the nearly accordant testimony of no less than 

 three reporters, whose judgment I have no means of testing; they agree 

 in giving 1864 or 1865 as the date of the first appearance of the butterfly 

 in eastern Pennsyh-ania, and a fourth refers to it hesitatingly, perhaps as a 

 matter of report ; it is possible that it might have been brought across the 

 ocean direct to Philadelphia at that date, but that it did not attract the 

 attention of other entomologists in and about Philadelphia, or make its 

 impression on the country around, renders the su])position highly im- 

 probable ; nor do the facts given above, regarding its spread about New 

 York, lead us to admit that it reached that city from Philadelphia. It is 

 far easier to suppose either that a mistake was made by each observer in 

 the species concerned, or that the memory was at fault, — all these state- 

 ments coming to me in answer to my direct enquiries ; none of them are 

 printed records. 



In conclusion, it may be remarked that the definite setting down of ter- 

 ritorial limits to each year's spread will naturally raise the question in the 

 mind of every lepidopterist who examines the map, whether it rightly in- 

 tei'prets the matter for the ground with which he is familiar. I beg, 

 therefore, to ask those who see reason to question the accuracy of the lines 

 at any point kindly to give me the benefit of their better knowledge, by 

 exact and detailed statements, and, whei'C possible, founded on something 

 better than memory. Should a sufficient number of important diver- 

 gences come to light, I will make them public in a forma! statement. It 

 may be stated, in a general way, that the lines are more conjectural in the 

 southern states than elsewhere, owing to the paucity of observations. 



%• See my paiier (Mom. Bost. sno. nat. bist., iv, No. 3) for full authorities for the statements 

 given above, principally derived from a large correspondence. 



Tabid of species of Pieris, base'! on Iheegg. 



Tapering distinctly ahove over the entire upper half oleracea. 



Tapering distinctly above only on the uiijier third rapae. 



