164 
Psyche 
[Vol. 90 
numerous “worker”, female and male brood.' Other things being 
equal, it might have been expected to have attained considerable 
genetic homogeneity, since new generations of “workers” and young 
queens were fathered exclusively by males reared within the colony. 
On November 4, 1979 this population was divided into two 
roughly equal halves and placed in separate arenas standing side 
by side on the same laboratory bench. All conditions were kept 
constant for the two moieties, designated A and B, except that they 
were maintained on differing diets, comprising crickets and dilute 
honey water for A and mealworm larvae and dilute sugar water for 
B. Two years later, on November 7, 1981, a series of compatibility 
tests were run between pairs of individuals taken one each from the 
two halves and allowed to encounter one another in fingerbowls, as 
described earlier. These demonstrated only very limited incompati- 
bility, as reported earlier (Haskins and Haskins, 1979), and sug- 
gested that diet, though possibly a measurable influence, was almost 
certainly not a critical factor in mediating compatibility as charac- 
terized in this test procedure. 
Individual pair-tests after isolation on the same diets 
On November 1 1, 1981 a further separation of the population was 
made by dividing Moiety B into two, designated B' and B'\ and 
continuing to maintain both on the identical diets of mealworms 
and sugar water, and continuing with no worker interchange or 
communication between them. They were held in this manner for a 
further year. Then, on November 15, 1982, fifty pair-tests were run 
between Moieties B' and B". In all but two of these pairs, full 
compatibility was exhibited in the fingerbowl trials. The same tests 
run the next day, November 16, between members of one of the pair 
of moieties maintained on the same diets {B' and B"), and the first 
moiety. A, still maintained on crickets and sugar water, showed 
' In /?. metallica reproduction occurs exclusively through fertilized ergatogynes which 
may make up from 5% to as much as 15% of the colony population and are morpho- 
logically indistinguishable from unfertilized sister workers. Thus reproduction is 
continuous and self-sustaining. Colonies are thus characteristically highly polygy- 
nous, and may persist nearly indefinitely under laboratory conditions. “True” 
females, fully winged and otherwise morphologically typical, can also be produced 
(and frequently were in the present population) but they seem to be without repro- 
ductive function, soon dealating themselves, functioning briefly as workers, and 
dying in a short time. 
