Psyche 
[March 
162 
for two colonies, and not quite significant at the 5% level for the 
other two (Table III). 
A log-log plot of allometry in colony 731 is shown in Fig. 2. The 
lack of alignment of the computed linear regression lines suggests 
that the dimorphism in this species may have arisen out of triphasic 
allometry with a dropping out of intermediates (Wilson 1953). 
Discussion 
The positive allometric growth of the first abdominal tergite in 
queens probably has an adaptive significance for the reproductive role 
of this caste. The expanded width of this segment reflects a general 
increase in size of the gaster (Fig. 1), which is most easily explained 
as an adaptation to accommodate the well-developed ovaries. Blackith 
(1958) found a similar increase in body proportions toward the pos- 
terior of queens compared to workers for two species of V espula. 
The negative allometry of the first abdominal tergite in workers 
must have other causes, however. It is possible that the narrower, 
more petiole-like first segment in workers may permit a greater 
maneuverability of the gaster and hence the sting, a feature that 
could in turn be interpreted as an adaptation to the role of workers 
in defense. Presumably the evolutionary divergence of the two castes 
with respect to this character reflects an almost complete functional 
sparation of the reproductive and defensive roles. 
The variance of the width of the first abdominal tergite given the 
length of the alitrunk is higher than that for ants (Wilson 1953). 
It resembles more closely the variance for certain halictine bees 
(Knerer & Atwood 1966). These differences may reflect a genetic 
component to the variability observed. In mononogynous ants all the 
workers of a colony are offspring of a single queen, and quite likely 
of a single male. In S. areata , however, since the colonies are 
polygynous, the individuals sampled do not all have the same parents, 
and thus represent a larger pool of genetic variability. 
A comparison of the degree of polymorphism shown by S. areata 
with that of other vespids is of interest, though difficult because of 
the lack of comparability of measurements used from one study to the 
next. The Vespinae are biometrically the best known social wasps 
(e.g. Wright, Lee, and Pearson 1907; Thompson, Bell, and Pearson 
1910, 1911; Blackith 1958). They also show the greatest degree of 
polymorphism. Blackith’s results for V espula germanica and V. rufa 
are probably typical (Blackith 1958). For the sake of comparison let 
