6 



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 Lasius niger americanus 

 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 Solenopsis molesta Say, 

 also a few dead males of Formica fiisca var. sitbsericea 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 Creuiastogaster lineolata Say 

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

 of Solenopsis molesta flying, many of them in copula. September ig, 

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

 females of Lasius niger aniericanus 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 



