88 
drive tunnels in the hard sandstone subsoil. The sandstone, however, 
must appear to the ants as lilliputian masonry, the stone being repre- 
sented by the sand grains, the mortar by the yellow clay which binds 
them together. It is not a question of cutting through the tiny bloeks 
of silica, it is only necessary to moisten the clay matrix with saliva 
and remove the loosened grain. Lafeadio Hearn’s statement that ants 
can bore tunnels in the solid rock is therefore seen to be misleading. 
Wm. M. Wheeler states his belief that the relatively large nest opening 
is an adaptation for increasing the ventilation.t My own view, based 
upon observation, continued for many months, is that the large en- 
trance is required for 
the removal of nodules 
of iron encountered 
while excavating. Dur- 
ing the hot weather of 
July and August the 
entrance was almost 
entirely blocked up 
with little clods; but 
when the first autumnal 
rain fell, softening the 
soil and favoring exea- 
vation, the hole was en- 
larged to a size some- 
what greater than that 
of a ten-cent piece 
(which measures eight- 
een millimeters, in di- 
ameter). (See fig. 3.) 
Six or eight workers 
unite their efforts to 
drag out a nodule. 
- 
Fig. 3. Nest entrance of Myrmecocystus mexi- Hach erasps if On dis 
canus mojave, with a ten-cent piece (18 mm. ne Lae ne oe 
dia.) for comparison, A winged female equatorial line with her 
lies on the coin. : : 
mandibles, and _ their 
bodies radiate outwards from this center like the spokes of a wheel 
Those in front drag, while those behind push, and after very heavy exer- 
tions the heavy burden is deposited outside the entrance. To allow egress 
for a team of eight workers surrounding a nodule necessitates a com- 
modious gangway. The constant stream of ants circulating through 
the galleries is probably sufficient to prevent the accumulation of stag- 
nant air. The nursery chambers are invariably situated in the upper 
+Ants, Their Structure, Development and Habits. Page 375. 
