THE SPREAD OF A BUTTERFLY IN A NEW REGION. 1185 



tended into North Carolina, though we have no report from there until 

 187^(, when Mr. W. V. Andrews found it in March at Asheville. The 

 southern part of our line for this year is, therefore, purely conjectural, as 

 are also the lines for the southern colonies, from which we have no data. 



There enters now a good deal of confusion in the dates of its appearance. 

 The insect had become abundant on all the main railway lines running east 

 and west and washable to be forcibly carried in any direction. Wherever 

 a pair, male and female, happened after all vicissitudes to come together, 

 there would be the point for the introduction of a new colony ; for migno- 

 nette or cabbage or turnip would be found somewhere about ; and the only 

 wonder is that the movement of the throng was as resrular as it was. 



During 1876 it covered the whole of western Ontario and extended into 

 eastern Michigan ; Mr. E. A. Strong even states that he took it at Grand 

 Rapids in 1875, but this I think must be a fault of recollection. Below 

 the Lakes, however, it moved on more rapidly. It is possible, if not 

 probable, that one of the roadside colonies to which I alluded above was 

 established in central Indiana before this, for Mr. S. G. Evans says that 

 Pieris rapae was common in Evansville when he began collecting there 

 in 1874; and Dr. G. M. Levette writes from Indianapolis, "From 

 recollections of myself and others I would place it [the introduction at 

 that point] in 1872 or 187;i." We have the very definite statement from 

 Dr. F. AV. Goding that he captured a female in his father's garden in 

 Kane Co., 111., 44 miles west of Chicago, on September 17, 1875. A 

 few days afterward, as he now distinctly remembers, he saw several in 

 cabbage fields west of Chicago, flying in company with protodice. Mr. 

 J. W. Huett also writes that he first saw the butterfly at Farm Kidge, 

 LaSalle Co., in the spring of 1874 or 1875, in scanty numbers. It would 

 therefore appear highly probable that, a year or two in advance of its 

 normal rate of progress, as if it had caught the fever of its surroundings, 

 Pieris rapae swept into Chicago on a railway train. We have no further 

 record for this year of the advance of the great horde, but simply from 

 analogy and subsequent facts, the curve of its probable progress has been 

 placed on the map. 



In this year, however, we have indications of the spread of both of the 

 southern colonies, for in October Dr. A. Oemler detected the butterfly at 

 Wilmington Island, off Savannah, — evidently an extension of the Charles- 

 ton colony of 1873 ; while the fact that the butterfly was as common in 

 1876 as now, at Lumpkin in the southwestern part of the state, indicates 

 the spread of the Apalachicola colony. 



In 1877, to begin now with the south, these two southern colonies prob- 

 ably merged, for the butterfly was common at Macon, a point which 

 probably might have been reached by either colony this year, though not 

 by the northern horde for a year or two later, to judge by all accounts. 



■49 



