THE HABITS OF ANTS IN GENERAL. 191 



they' have descended from the nuptial flight, for we often find more 

 than one queen in a colony. In some species of Formica a single colony 

 may thus accumulate more than fifty dealated queens. Certain obser- 

 vations also show that colonies may multiply by fission, the offshoots 

 migrating to new nests and taking with them some of the queens. 

 These nests may remain connected with the parental colony by run- 

 ways, but in some cases (Formica c.rscctoides) they probably become 

 independent commonwealths. This whole subject, however, is in 

 urgent need of careful investigation, as it has important bearings on 

 some of the cases of symbiosis to be described in future chapters. 



The number of ants in a colony varies greatly according to the 

 species, and evidently depends on the number and fertility of the 

 queens and the nature and amount of the available food. In many 

 species, like most Ponerinas, and the ants of the genera Leptothorax, 

 Cardiocondyla, Xcnomynnc.v, etc., among the Myrmicinse, the colony, 

 even at the apogee of its development, comprises only a few dozen, or 

 at most, a few hundred individuals. But the average nunrber for most 

 species is much greater and may exceed a thousand or ten thousand. 

 It is, however, very easy to overestimate the population of a colony. 

 Forel (1874) estimated that a Formica pratcnsis mound of medium size 

 contains 114,000 ants and that the largest formicaries may contain as 

 many as 500,000. But Yung (1899, 1900) who has actually counted 

 the ants in several hills of F. ntfa, an ant which has larger colonies 

 than pratcnsis, found the numbers to vary between 19,933 anc ^ 93^94- 

 These numbers are not proportional to the size of the nest. He, there- 

 fore, believes that Forel's estimates are excessive. Pricer ( 1908) has 

 recently given valuable statistics of Campanotus pennsylvanicus colo- 

 nies from their inception to their adult stage, which is marked by the 

 throwing off of males and virgin females. He finds that such adult 

 colonies contain from 1,943 to 2,500 workers, and that they must be 

 from three to six years old before they produce the sexual phases. 

 It is very probable that the population of the adult ant colony, which is, 

 after all, merely an enlarged family, fluctuates about a specific average 

 or mean. With the exception of Pricer's work, no attempts have been 

 made to determine this mean for our various species or its relation to 

 the ethological environment. Here is a promising field for statistical 

 study. 



