1971] 
Erickson — Displacement of Native Ant 
263 
Table 2. Food resources of I. humilis compared with species it has 
displaced throughout the world. 
Main Degree of 
Species 
Food Source Omnivory 
Reference 
Iridomyrmex humilis Mayr 
sweet or fatty 
foods, tends 
aphids scale 
insects, grains 
+ + + 
Wheeler, 1910 
Eckert & 
Mallis, 1937 
Creighton, 1950 
Skaife, 1961 
*Pogouomyrmex calif ornicus 
Buckley 
seed gatherers 
+ 
Wheeler, 1910 
Forel, 1928 
Wildermuth & 
Davis, 1931 
Cook, 1953 
Van Pelt, 1966 
Cole, 1968 
Phe'.do'e megacephala F. 
sweet or fatty 
foods 
+ + + 
Wheeler, 1910 
Forel, 1928 
*Pheidole grallipcs Wheeler 
seed gatherers 
+ 
Eckert & 
Mallis, 1937 
Cook, 1953 
*V eromessor pergandci Mayr 
seed gatherers 
+ 
Eckert & 
Mallis, 1937 
Cook, 1953 
Solenopsis saevissima Forel 
insects, fruits, 
grains, flowers, 
vegetables 
+ + + 
Creighton, 1950 
Cook, 1953 
Solcnopsis geminata F. 
insects, fruits, 
grains 
+ + 
Creighton, 1950 
Fluker & 
Beardsley, 1970 
^Displaced in present study. 
+ d~ T zzr highly omnivorous; + + = moderately omnivorous; + =: 
slightly omnivorous 
Should a harvester ant come upon an Argentine ant during the 
warmer parts of the day, the former grasps the smaller ant with its 
mandibles and stings it to death (Michener, 1942). At dawn, sun- 
set, or on a cloudy day the Argentine ants will attack and cling to 
the mandibles, legs, and antennae of the harvester ants and attempt 
to kill the larger ant. Observations made in the present study con- 
firm Michener’s discussion of the aggressive actions between the spe- 
cies. 
There were no significant differences in the mean monthly tem- 
perature or precipitation from month to month (i.e. — all the Janu- 
arys, etc.) over the course of the study. The vegetation studies 
