120 Psyche [August 
NEW SOCIAL BEES. 
By T. D. A. CockERELL, 
University of Colorado, Boulder, Colo. 
A close study of the Neotropical social bees of the genera Meli- 
pona and Trigona brings out the fact that there are numerous 
local races or subspecies, such as may be found among the ants. 
Most of the new forms coming to light are so closely related to 
others previously described, that 1t becomes a matter of conven- 
ience or opinion whether to regard them as distinct but closely 
related species, or races of aggregate species. Two or more of these 
closely related forms may occupy the same general region, and on 
the other hand, any one of them may extend over an enormous 
territory. They do not seem to be closely related to any special 
environmental factors, but they do follow the lines of general 
variation in the group, showing greater or less intensity of color or 
extension of color-pattern. They are practically constant in any 
one lot, and we do not find much miscellaneous individual variation. 
All this so closely parallels the condition among the ants, that we 
naturally look for a common cause or factor, which can only be the 
social mode of life, with continual inbreeding. In both groups, it 
is probably rare for individuals to mate with others than members 
of their own colony. Following up this idea, we note a similarity 
between the relationship of the different forms and that to be ob- 
served between these occupying a series of small islands; e. g., the 
birds of the Lesser Antilles, or the rats of the small islands of the 
Malay Archipelago. Continual inbreeding within a limited group 
or area will lead to homozygosity, and small differences in the origi- 
nal constituents may appreciably affect the end result. An occa- 
sional cross between stable races thus established will break up the 
combinations and furnish material for a series of new types. 
It must be said, however, that in Bombus we do not observe the 
same state of affairs. The species of Bombus are notoriously 
variable in color, and the varieties are largely local, but they are 
also largely individual. In Bombus, if I rightly understand the 
facts, the odoriferous males assemble from various nests, and do 
not necessarily or perhaps more than frequently mate with mem- 
bers of their own colony. If this is true, we can see why there is 
