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[June-September 
were never observed performing any defensive or “working” be- 
havior. They were recorded as using almost half of their time doing 
trophallaxis or offering infrabucal pellets to minors and medias. 
King and Walters (1950) have found a very similar situation in 
“Formica rufa melanotica” (=F. obscuripes) in natural nests. They 
were able to prove a correlation between polymorphism and 
polyethism, showing that minor workers were specialized in attend- 
ing aphids. The major workers again remained inside the nest most 
of the time. 
On Table 2 one can notice that all the categories of F. perpilosa 
spend the same amount of time performing grooming behavior. The 
minors are almost exclusively responsible for several tasks grouped 
as “working” and the medias spend a more uniform amount of time 
performing each group of behavioral acts. 
Wilson (1953) proposed a model for the origin and evolution of 
polymorphism in ants. In 1971 he reviewed the ant caste system and 
said that five steps can be recognized in the evolution within the 
worker caste: monomorphism, monophasic allometry, diphasic 
allometry, triphasic allometry and complete dimorphism. 
Age polyethism is the responsible phenomenon for caste structure 
in monomorphic species, and the polyethic classes are sometimes 
referred to as physiological classes. Traniello (1978) reported an 
apparent lack of temporal division of labor in the primitive ponerine 
ant Amblyopone pallipes, which appears to have the most primitive 
caste system yet documented in ants. 
Monophasic allometry is the commonest manifestation of non- 
isometric growth. Studies on the division of labor in weakly 
polymorphic species showed a “by preponderance” division of 
labor, i.e., any given worker should be capable of performing any 
given normal task. 
In Formica polyctena size variation is weakly correlated with 
division of labor. The behavioral variation observed by Otto (1958) 
consisted mainly of age polyethism and individual peculiarities. 
Although the F. perpilosa subcastes were not divided using age 
parameters, I believe that age does not account for a large fraction 
of the total behavioral variation. 
Majors of advanced polymorphic ant species, especially com- 
pletely dimorphic species, where intermediates no longer exist and 
the two remaining classes are remarkably different in morphology, 
