1978] 
Brandao — Worker Caste of Formica perpilosa 
233 
(1953), the log-log anamorphosis afforded a linear regression of 
head length on head width. The equation is 
log L = .2795 - .8602 log W 
or, alternatively, 
L = 1.9033 W" 8602 
The coefficient of determination, r 2 is also .964, showing of course 
an excellent fit. 
I have chosen the following criteria for the definition of the 
categories of workers: minors, head width 1 mm or less; medias, 1 to 
1.4 mm; majors, larger than 1.4 mm. 
The majors represent only 6.6% of the nest population and their 
behavioral catalog comprises merely 1 1 behavioral categories. Their 
behavior, as seen in Table 2, is mostly directed toward grooming 
and regurgitation with nestmates. 
Discussion and Conclusion 
The behavioral catalog and the head shape curve of our Formica 
perpilosa colony show that the worker caste is strongly polyethic, in 
spite of being only slightly polymorphic. The media category is 
responsible for most of the behavioral categories. The majors are 
specialized in regurgitation with nestmates and may act as a trophic 
subcaste as in Camponotus (Colobopsis)fraxinicola (Wilson, 1974). 
F. perpilosa majors also possess a relatively large abdomen and 
Table 2. Relative frequencies of groups of behavioral acts listed on Table 1 by 
the three worker subcastes in a single colony of Formica perpilosa. (N. total 
number of behavioral acts recorded for each subcaste.) 
Groups of 
behavioral acts 
(from Table 1) 
A — Grooming 
B — Brood Care 
C — Regurgitation 
D — “Working” 
E — Jittering & Antennal tipping 
minor 
media 
major 
workers 
workers 
workers 
N = 996 
N = 1679 
N = 134 
.365 
.390 
.380 
.137 
.248 
.134 
.127 
.241 
.486 
.355 
.116 
0 
.017 
.002 
0 
1.0 
1.0 
1.0 
