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the ants clustering around and over them in a way to conceal them 
from view. When the colony is established in a two-celled nest, one 
covered with clear glass and the other with orange, the workers con- 
vey their young to the orange cell, the light transmitted by orange 
glass being, as shown by Miss Fielde. inappreciable by ants. 
Even after the workers have emerged from the pupa-case they 
are still watched and cared for by their more experienced relatives, 
and often fed in the nest by foragers returning from outside. This 
operation was illustrated in our breeding-cages when pale young 
workers remaining within the orange cell were fed by the darker, 
older ones from food exposed to them in the light cell of the formicary. 
The nursing instinct of the workers is so overruling that it ex- 
tends to all the inmates of the nest excepting only strangers of their 
own species. A common resident of the nest of these ants is a species 
of mite (Macrocheles moestus Banks) often found crawling about 
among the eggs and larvae, altho never detected in any depredation 
upon them. It is probably a scavenger of the domicil, and is thus 
possibly entitled to the protection which it receives. When a nest con- 
taining these mites is disturbed, they receive the same attention as its 
other inmates from the alarmed and anxious workers. In several 
nests for example, plowed up April 24, in an old oats field, mites were 
commonly present, and the ants seized them in their mandibles and 
carried them away as they did their own young. 
Adaptation of Behavior to changing Conditions 
The movements of ants in their outdoor habitations often show 
a surprising adaptation of habit and behavior to changing conditions 
in the field. It was repeatedly noticed, for example, that during warm 
dry weather in early spring the aphis eggs would often be brought 
near the surface while the larvae of the ants were kept at a depth of 
five or six inches below. The effect of this treatment must be to 
hasten the hatching of the aphids and at the same time to retard the 
development of the larvae of the ants. The growth of the latter is thus 
kept practically at a standstill while food is scarce in spring, but pro- 
ceeds at a rapid pace after the aphids have hatched and are yielding 
an abundant food supply to the colony. In periods of summer drouth 
the burrows are extended downward to a depth of twelve or fifteen 
inches, and eggs, larvae, and pupae are carried down into relatively 
moist earth. The ants then mass up in the depths of their burrows 
and are rarely seen abroad, but communicate with their root-louse 
herds by means of underground passageways, sometimes several feet 
in length. When soaking rains come, these hidden colonies open up 
their burrows to the surface again, as the ground dries off, and resume 
their more active habits as general foragers. 
Under certain conditions of serious deprivation and suffering, 
however, this whole system breaks down, and the ants may devour, for 
their own temporary maintenance, the very objects to which they have 
previously devoted their entire existence. When infested plants wither 
