1911] The Ottawa Naturalist 129 



ABUNDANCE OF THE COTTON MOTH IN ONTARIO. 



By Arthur Gibson. 



In the Province of Ontario there occurs periodically, in 

 autumn, conspicuous nights of the southern Cotton Moth, 

 Aletia argillacea. During September, 1911, an extraordinary 

 flight of these moths was observed in Western Ontario. Mr. W. 

 A. Dent, of Sarnia, Ont., reports that on the evening of September 

 15th "these moths arrived at Sarnia in countless numbers, for 

 underneath the electric lights in various parts of the town, the 

 ground was covered several inches deep, and for a space of 

 several yards in diameter with their bodies." At St. Thomas, 

 Ont., immense swarms of the moths were also present and 

 attracted a good deal of attention. Mr. S. J. English reported 

 that on September 30th "they were in heaps all along the 

 principal street Talbot Street and in other parts of the city." 

 Similar flights were also observed in the United States. In 

 Science, Oct. 13th, 1911, Dr. H.T. Fernald reports that the moths 

 were rather abundant, during the last week in September, at 

 Amherst, Mass., and Dr. Henry Skinner, in Entomological News, 

 Nov., 1911, states that "from September 23rd to 26th, Phila- 

 delphia experienced a large flight of the Cotton Moth, Aletia 

 argillacea. They swarmed in some parts of the city and hundreds 

 were resting head down on the electric light poles and on plate 

 glass windows of stores. There were many thousands of them 

 and nearly all that I saw were in perfect condition as though 

 just from the chrysalis. These moths are known to migrate in 

 numbers, but it is quite strange if the great numbers seen here 

 came from the cotton districts in the south. The moths in some 

 places appeared to create considerable alarm, people thinking 

 they would cause damage to plant life here." 



The occurrence of this moth in noticeable numbers in Canada 

 is by no means rare, but its appearance during the past autumn in 

 such excessive numbers, as observed in widespread districts, is 

 indeed remarkable. In September last the moths were present 

 in the Ottawa district, but were not abundant. In other years 

 they have, however, been very common in this latter locality. 

 In 1887, Dr. C. J. S. Bethune records * the moths as having 

 occurred in large numbers at Port Hope, Ont., on October 7th 

 to 10th. During the same year they were abundant at Ottawa, 

 when on October 10th, Mr. W. H. Harrington saw at least 

 2 50 or 300 upon the front of the Bank of Ottawa building, 

 opposite Parliament Square. During the same year immense 



Eighteenth Annual Report, Entomological Society of Ontario. 



