418 



collecting, that during August the percentage of nests containing 



winged forms decreases, so that it is very probable that the flights 



begin during that month in this latitude. September 5, 1910, I found 



a large number of young dealated females of Lasiiis niger americaniis 



crawling on the ground in a park in Boston, Mass. This was about 



five o'clock in the evening. They had all removed their wings, and 



were crawling around in search of a place to burrow. A number were 



already beginning their burrows. At one place I saw six beginning 



to burrow in the same place. There were also many males flying in 



the air or crawling about, but I saw no couples in copula. The same 



afternoon I found five young dealated queens of L. latipes Walsh, a 



number of winged and dealated females of Solcnopsis molest a Say, 



also a few dead males of Formica fitsca var. suhscricca Say. This 



fact indicates that weather conditions probably determine to a large 



extent the time of a flight. There had been a heavy rain the day 



before, but on that day it was clear and very warm. The following 



day, September 6, with the same weather conditions, I found a large 



number of males and winged females of Crcmastogaster lineolata Say 



crawling about on the walks, and two days later I saw a large number 



of Solcnopsis molest a flying, many of them in copula. September ig, 



1910, and on almost every day for the next ten days, I caught winged 



females of Lasiiis nigcr americaniis flying or saw the young queens 



crawling over the ground. On the evening of October 4, I found five 



winged and sixteen dealated queens of L. niger americanus crawling 



on the ground, one dealated queen October 11, and one October 18. 



The fact that dealated queens of this species are found crawling about 



is evidence that there has been a flight, since these queens begin to 



burrow immediately after descending from their flight and do not 



come to the surface again. 



The dates upon which I have actually witnessed the flights of 

 L. americanus from the nest are September 9, September 20, and 

 September 18. All the flights of this species I have noticed have been 

 between 3 p. m. and 6 p. m. The best observations were obtained 

 from the one of September 20. In this case the entrance of a large 

 nest was near the edge of a cement walk. At 4 130 p. m. my attention 

 was called to the fact that a very large number of ants were crawling 

 over the walk and grass near the opening. Closer examination showed 

 that there were many males, winged females, and workers there, all 

 running about excitedly, and that every few minutes a male or female 

 rose from the blades of grass or the walk and flew away. They did 

 not all fly away in the same direction, but seemed to take whatever 



