No. 417.] NESTS OF AMERICAN ANTS. 723 
exsecta, has dulotic proclivities which are shown only while the 
colony is young. In this connection the above-recorded fact, 
that weak colonies of F. sanguinea are found to have the most 
slaves, is perhaps significant. 
28. Dorymyrmex pyramicus Roger, vars. niger Forel and flavus 
McCoo 
A peculiar mixed colony containing both the common vari- 
eties of Dorymyrmex pyramicus was found by Forel at Faisons 
N.C. (00°, p. 5). * There were two or three nests situated 
several meters apart. The yellow workers and the black 
workers entered and went out peaceably side by side, worked 
together and treated one another with every show of friend- 
ship. The two forms were, nevertheless, perfectly distinct, 
without presenting any transitional varieties. I completely 
demolished one of the nests and had the good fortune to find 
the females and males of niger and the male of flavus, the 
latter being larger and paler."  Forel believes that this nest 
arose “without doubt by the fortuitous association of two 
fertile females, one of each variety." He therefore regards it 
as of the same nature as the peculiar mixed nest of Tapinoma- 
Bothriomyrmex which he described in the * Fourmis de la 
Suisse ” (74, p. 372). 
29. Pogonomyrmex barbatus Smith and its var. molifaciens Buckley. 
At Aguas Calientes, Mexico, Dec. 31, 1900, I happened on 
a huge gravel cone nest of the agricultural ant (Pogonomyrmex 
barbatus), containing about equal numbers of the typical species 
(with black head and thorax) and the entirely red var. molifa- 
ciens. There were no transitional varieties. Both forms were 
living together on the most amicable terms. As I entertained 
little hope of finding the queens, since this would, in all proba- 
bility, have required a very careful excavation of the soil to a 
depth of from five to eight feet, I had to rest satisfied with dig- 
ging into the nest a short distance and examining the hosts 
of belligerent workers that swarmed forth. As this was obvi- 
ously an old and very flourishing colony, there can be little 
