No. 417.] NESTS OF AMERICAN ANTS. pet 
The fact that these mixed nests rarely contain male Tetramo- 
riums and never, so far as known, queen pupz of this species, 
is explained by Forel (00%, p. 273) as the result of a general 
regulative instinct : * The females and males of Strongylog- 
nathus are smaller and less troublesome to nourish. This is 
obviously sufficient to induce the Tetramorium workers to rear 
them in the place of their own enormous queens and males, 
the larvae of which they therefore undoubtedly devour or 
neglect, as they do in the case of all that seems to be super- 
fluous."' 
After this brief review of the European species we may turn 
to our American dulotic ants. 
16. Formica sanguinea Latr., subsp. rubicunda Emery. 
Although the typical F. sanguinea is not known to occur in 
America, the species is, as Emery has shown (932, p. 647), far 
more variable on this continent than it is in Europe. We 
should therefore be prepared to find a corresponding variability 
in its instincts, though this may not be commensurate with its 
taxonomic variation. 
F. sanguinea is also occasionally found without slaves in 
America, but far more frequently it is attended by ants belong- 
ing to the great group of forms which centers about F. fusca. 
The best known subspecies of F. sanguinea in the Northern 
and Atlantic States is undoubtedly rubicunda. This is usually 
found with slaves belonging to F. fusca, var. subsericea Say, but 
one colony which I observed near Rockford, Ill, Sept. 16, 
1900, contained about equal numbers of auxiliaries belonging 
to two species, viz. F. pallide.fulva Latr., subsp. nitidiventris 
Emery, and F. fusca, var. subenescens Emery. 
The above assumption that the habits of /. sanguinea in 
America may differ to some extent from those of the European 
form seems to be borne out by some recent observations of 
Forel (00v, pp. 11-12). Owing to Forel's long and very inti- 
mate acquaintance with the European sanguinea, these obser- 
vations on our American form are of great value. He had 
Occasion at Cromwell, Conn., to witness the attack of a very 
