40 Bulletin American Museum of Natural History. [Vol, XXII, 



formicaries. During the past May (1905) I observed an unusually 

 striking case of colony formation by queens of the Californian har- 

 vester {Pogonomyrm.ex calif amicus) on the edge of the Mojave Desert. 

 This observation recalls the above quoted passage from Lincecum on 

 the Texan harvester. I arrived at Needles, California, May 23, a day 

 or two after the nuptial flight of P. calif amicus. This was proved by 

 the thousands of isolated females of this species, in the act of establish- 

 ing their formicaries. The country in which I observed them was the 

 sandy bottom on the right bank of the Colorado River and the adjacent 

 low escarpment of the desert. The latter is interrupted by numerous 

 short ' draws,' which are more or less sandy like the river bottom into 

 which they open. The surface of the escarpment, however, is very 

 hard and stony, but it, too, is furrowed by very small ' draws' often 

 only a few inches wide and containing sand washed from the surround- 

 ing surfaces by the winter showers. After their nuptial flight myriads 

 of Pogonomyrm-ex females had rained down over the whole hot, dry 

 country for a distance of at least three miles to the south and as many 

 to the west of the Needles. After losing her wings, each female sought 

 out the regions of pure sand, avoiding the hard surfaces, and set to 

 work digging a hole. The earth was brought out to one side of the 

 burrow so as to form a diminutive fan-shaped mound, which when com- 

 pleted was about two inches in diameter (PI. VIII, Fig. 2). On May 23, 

 during the hot morning hours the females could be seen at work every- 

 where in the 'draws ' and river bottom, often within a few inches of one 

 another. Manv had already completed their burrows, which extended 

 down obliquely to a depth of three or four inches, and had closed the 

 opening behind them. It was an easy matter to dig a dealated female 

 from each spot indicated by a small fan-shaped mound or to tempt her 

 to the surface by inserting a straw into her burrow. A wind- or rain- 

 storm would have obliterated at oace all traces of the whereabouts of 

 these females. That they actually sought the pure sand, which is also 

 the substance in which the adult colonies are found, was seen on the 

 top of the escarpment. There each tiny draw was literally filled with 

 incipient nests, although none could be found on the hard interven- 

 ing spaces often hundreds of feet wide. The ants would, in fact, be 

 quite unable to excavate in such hard soil. The comparatively small 

 number of adult colonies in the vicinity proved that but few of 

 these isolated females ever succeed in rearing a colony. They are 

 doomed to rigid, all but catastrophic, elimination, which only the best 

 endowed and most favorably situated can survive. 



In the foregoing paragraphs attention has been repeatedly called 



