84 
Psyche 
[Apri ] 
flattening, yet with depressions and recoveries. In a drawing 
showing the projections of the circumference of the mound as 
measured or calculated each year the circles enlarge concen- 
trically and rather uniformly at first and then, in this special 
case of the mound being erected upon unlevel base, the north- 
west-south-east diameter elongates and the outlines become 
more elliptical with the axis shifted to west of north. 
The curve of the bulk, as plotted from the calculated bulks 
at ends of years, shows steady rise for the first years; a de- 
pression in 1920 followed by greatly increased acceleration with 
a second set back in 1923 followed by a sharp rise above all 
previous heights. All these plotted results show irregularities 
which suggest complex factors acting upon the growth of the 
mound. The very slow growth the first years is striking as well 
as the very rapid growth in some later years correlated with the 
small numbers of ants in the incipient colony at first and the 
immense numbers in the old successful community. The ants 
work but half of the year at most, lying dormant in November 
to March inclusive. 
It is to be emphasized that the growth is very irregular, the 
only constant numbers in the table are the interpolated figures 
in the seven years when measurements were not actually made. 
While some of these irregularities are due to crude measure- 
ments many seem to be the results of complex factors and they 
actually may express the resultant of causes of success or failure 
in the community. Thus in the years of no progress and of 
actual diminution, the loss of height is sometimes compensated 
by increase in width since the materials are spread out laterally 
in place of b3ing accumulated at the apex; but there is some- 
times an actual dimunition in bulk. As the interior of the 
mound is spongy and readily compressed by large animals walk- 
ing on the mound it sometimes happens that the measured bulk 
may diminish when the mass is the same or greater. Possibly 
some storms may actually carry material in some quantities 
away from the nest so far that it is not soon returned by the 
ants and thus the mound may be washed away if the ants are 
not very successful some seasons in combatting this constant 
denudation. When a mound is deserted it slowly dwindles 
