-Jyo ANTS. 



other colonies, wliicli had celebrated their nuptial flight the day 

 before, revealed the same conditions. It is certain, therefore, that 

 i he nialci'icicns colonies do not throw off all their males and 

 females during the nuptial flight, and are thus able to avoid a com- 

 plete destruction of the annual sexual generation. This conclusion 

 is also borne out by the observations of Mr. W. H. Long, Miss A. 

 Ruckcr and Miss M. llolliday, who witnessed several minor nuptial 

 flights during the latter part of the summer (August 6-10). I have 

 also seen mature males and winged females in the nests in March and 

 April, so that there are probably small flights also during the spring 

 months. l>ut unlike many other ants, inolcfacicns does not dealate 

 and permanently detain in the nest a number of females in addition 

 to the mother-queen that originally established the formicary. At any 

 rate, I have never been able to find more than one dealated queen in a 

 colony, which, therefore, occupies only a single nest. This is also true 

 of the other species of Pogonomyrmex that have come under my 

 observation. 



The formicaries of inolcfacicns are founded in the same manner as 

 those of P. calif ornicits described in a former chapter. As Lincecum 

 was the first to observe, the recently fertilized female digs down into 

 the soil to a depth of about 15 cm., closes the opening after her and 

 gradually brings to maturity a brood of about a dozen very small and 

 timid workers. During the following -spring the workers open the 

 nest to the surface, but are always careful to keep the entrance hidden 

 under a few sticks or pebbles, which have the appearance, as Lincecum 

 says, of having been drifted together by the wind (Fig. 161). It is not 

 till the second year, when a number of large workers have been pro- 

 duced, that the ants begin to cut down the vegetation around the nest 

 entrance, now left fully exposed, and to establish their circular disk, 

 which is continually enlarged as the number of workers increases. On 

 the deserts east of Alberquerque, New Mexico, I saw a number of 

 incipient colonies of P. nigosns in the act of cutting down young 

 Astragalus plants and clearing disks about 30 cm. in diameter (Fig. 

 162). The further development of the nest differs with the character 

 of the soil. \Yhere this is an even adobe or sandy loam, no crater is 

 constructed, but the disk is merely enlarged. In localities where there 

 are many pebbles scattered over the soil, these are assiduously collected 

 and built into a crater (Fig. 158). The cleared disk is obviously an 

 adaptation for securing the maximum amount of dryness for the 

 granaries in the soil, and although seeds are often stored in the crater 

 chambers, the latter seem to be of even greater utility in incubating the 

 brood. The larva?, as in E. imbcrbiciiliis, are fed with pieces of 



