1965 ] Haskins and Whelden — Rhytidoponera 105 
abnormality in embryonic development. Examination of 119 eggs 
from the two colony fragments showed the greater number to be 
uninucleate. A few contained 2-4 small nuclei, tending to be clumped 
abnormally at one pole of the egg. In a very few cases embryonic 
development was sufficiently advanced to show some segmentation and 
to indicate the polarity of the embryo, but this was all. By contrast, 
a control sample of eggs taken at the same time from a colony housed 
and treated in the same manner but much more recently collected 
showed clear evidence of development in over 80 per cent of ova 
examined, ranging from early stages showing masses of well-defined 
cell nuclei to late and well-formed embryos. 
Such evidence suggests that the maintenance of a rather high degree 
of female heterozygosity is no less a biological imperative for Rhyti- 
doponera than for Formicid species possessing alate queens and ex- 
hibiting highly organized mating and dispersion flights involving both 
sexes. Indeed, the evidence for multiple insemination of workers 
suggests that it may be considerably more dependent than some species. 
It seems probable that a system of sex-locus lethal or semilethal alleles 
exists similar to that described by Mackensen ( 1951 , 1955 ) and 
Rothenbuhler ( 1957 ) for Apis , and originally in Habrobracon by 
Whiting ( 1943). It would seem that such a requirement of heterozy- 
gosity, in the context of the kind of colony organization displayed by 
the “queenless” species of Rhytidoponera , must complicate the main- 
tenance of close genetic relationships among workers within a colony. 
THE FORMATION OF NEW COLONIES IN R. METALLICA 
Central to the problem of whether successive generations of fertile 
workers remain in older colonies is the question of how new colonies 
are formed. At present it is uncertain what may be the normal life 
course of young workers subsequent to fertilization in a parent colony. 
Some observations have accumulated, however, which may bear on 
the mode of formation of new colonies in R. metallica. 
Workers taken at random from established colonies in the artificial 
nest and isolated in new nests regularly attempted to initiate fresh 
communities. They secreted themselves in partly closed cells, from 
which they emerged occasionally to forage in the fashion typical of 
normal colony-founding Ponerine queens, laid eggs and tended them 
carefully, reared larvae, and in a number of cases matured adult 
progeny. Unfortunately, it has not so far proved possible to distinguish 
and select fertilized workers for these experiments, and all progeny 
reared by such isolated workers have been males. Had worker progeny 
been reared, however, a new colony might easily have arisen. 
Thus it seems at least plausible that isolated workers of R. metal- 
