1960 ] Creighton — Phcidole militicida 1 1 
is completely unlike its bumbling efforts elsewhere. This, plus the 
fact that these responses are repeated with surprising exactness time 
after time, and by majors from different nests, leads us to conclude 
that they are the normal guarding responses of the militicida major. 
If this is true the major of militicida is best regarded as a soldier. 
Its role in the harvesting activities of the colony is slight and it is 
not primarily a seed-crusher, as has been mistakenly supposed. 
The defensive activities of the militicida major probably account 
for the mutilated remains which Wheeler found when he discovered 
this species, for the defending majors do not always dispatch the in- 
truders without loss to themselves. This seems a more probable ex- 
planation than that proposed by Creighton and Gregg in 1955 (2), 
who suggested that the accumulation of dead majors discovered by 
Wheeler might have been a result of the high death rate of that caste 
during the peak of the harvest season. This now seems unlikely, for 
the death rate of the majors during the winter months has proved to 
be extremely low. Most of the fifteen colonies that we studied dis- 
carded no dead majors during the three months that they were 
under observation. Only four dead majors were placed on the chaff 
piles during this period. Each of these was carefully examined under 
a binocular microscope for signs of mutilation and each was found 
to be completely undamaged with not even a tarsal claw missing. 
This disposes of the last bit of evidence on which Wheeler based his 
hypothesis, for it is now clear that the minors of militicida neither 
kill the majors nor cut them to pieces after they have died. Thus 
Wheeler’s views of the habits of militicida have proved to be at total 
variance with what these habits actually are. 
In conclusion, it may be noted that militicida is a very difficult 
subject for investigations in artificial nests. This species is unusually 
sensitive both to temperature and humidity. Temperatures below 
freezing invariably kill the ants and they are almost as seriously 
affected by a heavy condensation of water on the glass of the nests. 
I hey seem unable to keep out of the water droplets and many of 
the minors die in them. They also die if the nest is too dry. This 
sensitivity made it difficult to maintain the captive colonies for any 
length of time. At the suggestion of Dr. Robert Chew, of the De- 
partment of Biology of the University of Southern California, the 
artificial nests were placed on a rack, in a covered aquarium, above a 
saturated solution of sodium chloride. In a closed system this should 
maintain a constant humidity of 78% of saturation regardless of 
temperature. The arrangement proved eminently satisfactory. It 
