136 
Psyche 
[September 
is very close to that of the crouching guard and may be in actual con- 
tact with it. Another advantage of the aquarium nests was that they 
permitted limited foraging. If free colonies of texanus forage as did 
those in the aquaria, then texanus forages only in the daytime. Forag- 
ing appears to be initiated by the morning increase in light intensity 
but it will not occur unless the temperature is 70°F. or higher. Much 
of the foraging was done by the medias and minors but the majors 
were not restricted to the nest. This led to another type of response 
when the major on guard at the nest entrance had to admit another 
major, for the usual crouching reaction of the guard will not furnish 
enough space to allow a major to enter. When this was necessary the 
guard came out of the nest entrance. The returning major then 
entered the burrow head first, after which the guard backed into the 
entrance and assumed the occluding position. In the aquarium nests 
the guard was not continually on duty. This may have been because 
no strange ants were present. The writer has observed the same 
behavior in Camponotus ( Myrmaphaenus) ulcerosus Wh. (2), whose 
major assumes the phragmotic position only when other ants are in 
the vicinity of the nest entrance. 
In our 1954 publication it was stated that texanus sometimes forages 
on the ground. This may be true but it is now clear that such foraging 
has not been conclusively demonstrated. The aquaria nests were kept 
supplied with fresh live-oak twigs and the ants constantly walked 
about on their leaves. Although texanus is not an agile ant, it is 
surprisingly sure-footed. Even so foraging workers would sometimes 
lose their balance and fall to the floor of the aquarium. When a 
worker lands on its back, as it often does, it rights itself in an un- 
varying fashion. Both the head and the gaster are lifted above the 
surface on which the ant is lying until the body forms an arc. There- 
after one of the hind legs is extended and the body is rocked until 
it turns on one side. In the scores of times that the ants were seen 
to regain their footing, the process never varied in the slightest par- 
ticular. While the flattened dorsum of texanus undoubtedly makes 
it difficult to right the body from an inverted position, this will not 
explain why the righting reaction is so stereotyped. But this unvarying 
righting reaction can be explained if the ants have had occasion to right 
themselves so often that the most efficient method of righting has be- 
come an integral part of their behavior. This implies that the ants fre- 
quently fall from the trees in which they live, a view that is supported 
by their actions in the aquaria. For if the ants cannot always maintain 
their footing on leaves that are unaffected by wind, then every strong 
