884 THE AMERICAN NATURALIST. [Vor. XXXV. 
the Mermis after they have developed as workers so far that 
their structure can no longer be affected except in volume, or 
that the still undifferentiated larvae are infested but neverthe- 
less develop into workers because so much of the food which 
they devour is appropriated by their parasites. A decision 
between these alternatives would require more precise study 
than was possible under the circumstances. 
While there can be no doubt that macroérgatism in Ph. com- 
mutata is due to the presence of the Mermis, we cannot with 
certainty exclude the possibility of an atavistic tendency 
towards macroérgatism in the workers of this genus; for, as 
Emery has shown in a very suggestive paper,! in those ants 
which have the sterile females represented by huge soldiers 
and diminutive workers, the latter have without doubt under- 
gone a reduction in size during phylogenetic development. 
It would be possible, therefore, to explain macroérgatism as 
an attempt to regain the ancestral worker stature which was, 
of course, that of the queen. This is probably the explana- 
tion of macroérgatism in many ants, e.g., in Solenopsis, and 
possibly also in the small group of Pheidole mentioned in 
the introduction to this paper. While a similar reversional 
tendency may also be present in PA. commutata, it is perhaps 
unnecessary to lay much stress upon it, since the presence of 
the Mermis is of itself quite sufficient to account for the 
stature of the macroérgates. 
It is interesting in conclusion to compare the production 
of macroérgates in the nests of Ph. commutata with certain 
phenomena observed by Wasmann? in mixed nests of Polyer- 
gus rufescens and Formica fusca. He finds that such nests 
are peculiarly liable to contain ergatoid females of the former 
species, Z.e.,, “individuals which in size and in the development 
of the abdomen (even of the ovaries) belong to the true female | 
type, but have the thoracic structure of the workers and are 
therefore wingless." From a biological point of view these 
are, as Wasmann claims, really secondary queens. He believes 
that they are produced by the slave ants (F. fusca) through 
! Die Entstehung und Ausbildung des TTEA bei den Ameisen, Biol. 
Centralll., Bd. xiv (1894), pp. 53-59. 2 Loc 
