4o6 Bulletin American Museum of Natural History. [Vol. XXII, 



the exsectoidcs nests is the fact that they show very clearly some of 

 the conditions which lead to their ultimate decay and abandonment 

 by the ants. Observations made near Scotch Plains, together with 

 those I have collected in some other localities (Staten Island, High- 

 land-on-Hudson, Colebrook, Conn.), show that these structures pass 

 through the following evolutionary and involutionary stages: 



1. The incipient nest. In a previous article^ I maintained that 

 nests of F. exsectoides may be established in two different ways: first 

 by the association of a recently fertilized female with workers of her 

 own species from the maternal or some neighboring colony, and the 

 emigration of the company thus formed, followed by the construction 

 of a new nest in a different locality, and second, by the association 

 of a recently fertilized female with an effete or queenless colony of 

 the common black ant (F. jiisca var. subsericea) . In the latter case 

 the female remains with the host species until her first brood of 

 workers matures and the host workers have perished. Then, the 

 object of this temporary parasition having been accomplished, the 

 pure exsectoides colony is able to multiply rapidly and without ex- 

 traneous assistance. In this, the earliest stage in the development 

 of the colony, the nest is, of course, that of F. subsericea, a low ob- 

 scure mound overgrown with long grass and perforated with numerous 

 entrances. Even when the colony is pure from the start, however, 

 that is, when a young female associates herself with workers of her 

 own species, the nest is of this same character as shown in my former 

 paper (antca, PI. XII, Fig. i). Similar nests were seen in the Scotch 

 Plains colony in close proximity to the large mounds. 



2. As the ants keep enlarging their nest it takes on a somewhat 

 different appearance. They deposit large quantities of earth and 

 vegetable detritus on the summit of the mound and kill off the grass 

 in this region, so that the mound comes to have a bare summit and 

 is surrounded by a broad belt of tall grass This grass belt, to which 

 the numerous openings of the nest are largely confined, is usually 

 thinned out by the ants to admit the sun's light and warmth to the 

 soil in which it grows. Two young nests of this description are 

 represented in my former paper {antea, PL XIII, Figs, i and 2). The 

 grass zone is occasionally retained until the nest reaches a large size. 

 This is the case in the one figured on PL LXIII, which is No. 11 of the 

 table on p. 404. 



3. Most nests, however, that have attained a large size and are 



1 On the Founding of Colonies by Queen Ants, with Special Reference to the Parasitic and 

 Slave-making Species: Bull. Am. Mus. Nat. Hist., XXII, 1906, pp. 33-i°S. pH- viii-xiv. 



