1983] 
Calabi, Traniello, and Werner — Pheido/e 
399 
Both castes exchange food with minors, but trophallaxis is rela- 
tively more important in the majors’ repertory. Though its actual 
frequency is low, it constitutes their only non-defense task, and it 
comprises 5% of the tasks they perform versus only 1% for minors. 
In fact, when all categories of trophallaxis by minors are combined 
(with majors, larvae, and the queen as well as with minors), trophal- 
laxis still comprises only 2% of the minors’ task repertory. This 
relative frequency of the behavior by majors led us to ask whether 
majors serve as a replete or “cask” caste, as in Caniponotus fraxi- 
nicola (Wilson 1974). Pheidole hortensis majors with full gasters 
show a three-fold weight increase, but we were unable to perform 
the critical experiments and test for proportionate weight gain. 
However, in random surveys of the colony, replete majors (those 
with distended gasters) performed virtually none of the behaviors 
typcial of majors (Table 2). During experimentally induced attack 
(assault with sympatric Tetramoriuni spp.), replete majors engaged 
in defense only if the attack was severe (many ants) or extended in 
time. How much of this inactivity by “storage” majors is due to 
protecting the food supply and how much to relative inability to 
move is not clear. 
Another potential set of caste differences relates to the granivo- 
rous habits of many Pheidole species in which minors harvest and 
majors mill seeds. In an attempt to observe such caste differences in 
P. hortensis, we offered grass, vegetable, and bird seeds of various 
sizes and fat contents. All were ignored by both physical castes. 
3. Division of labor by age classes within a physical caste. 
To answer this question, we tested the null hypothesis that each 
age class should perform a given behavior in proportion to the 
number of ants in that age class. Thus, in a colony with three age 
Patrol at Food 
Patrol Arena 
Attack Intruder 
Guard Nest Entrance 
“Replete” Majors 
12 
0 
I 
0 
Non-“Repletes” 
66 
8 
18 
20 
Table 2. Behavioral differences within the major worker caste of Pheidole 
hortensis. The numbers of individuals observed performing various acts during 
random surveys of the colony arc presented. 
