BIOLOGICAL STUDIES 



I. The Life History of the Corn-field Ant, 

 Lasius nigcr var. amcricaiius Emery 



Although the common corn-field ant, Lasius niger var. americanus 

 Emery, is said to be the most abundant of all North American insects, 

 its complete life history has never been worked out. The most that 

 we have on the subject is given in Bulletin 131 of the Illinois Experi- 

 ment Station by Forbes. He there reports that in four cases the first 

 eggs from young queens were obtained May 8, 9, 10, and 15 ; that the 

 egg periods were 16, 17, 19, and 23 days; that the pupal stage aver- 

 aged about 18 days; and that the total number of young produced by 

 a single female in the first year was in three cases 8, 9, and 19 work- 

 ers. The more extensive data which I have been able to obtain cor- 

 respond in great measure to those just given. 



methods 



The method followed in this life history study consisted (i) in 

 making observations in the field at all times of the year, (2) in mak- 

 ing daily observations on young fertilized and isolated females through 

 one season, (3) in isolating old queens from large nests and getting 

 counts of the eggs they laid, and (4) in keeping large colonies in 

 Fielde nests under daily observation. These young fertilized females 

 were obtained in the fall just after they had descended from their 

 nuptial flight, or after they had formed their cells ; or they were taken 

 from their cells in the spring before they had begun to lay eggs. They 

 were kept for the most part in Fielde nests of the ordinary type, or 

 in some cases in Barth nests. The latter are more satisfactory for 

 keeping the ants under natural conditions, but with them one can not 

 make as accurate observations regarding the exact number of eggs 

 and young. 



NUPTIAL FLIGHTS 



The nuptial flights of Lasius americanus usually occur from Au- 

 gust to September. The date of a flight mentioned by Forbes is 

 September 14. The earliest date for which I have positive evidence 

 of a flight is September 5. I have noticed, however, in a summer's 



