1983] 
Haskins & Haskins — Rhytidoponera nietallica 
169 
in a corner. Except for these three, no further attacks were wit- 
nessed. The other seven workers appeared to have been “adopted”. 
It is possible that the attacked workers were in fact egglaying indi- 
viduals, which may have stimulated the hostile attacks, as found by 
Holldobler (in litt.) for Novomessor in similar situations. 
Simultaneously the reciprocal introduction was performed. Ten 
workers of B' were introduced into the B" arena in similar fashion, 
at 3:45 p.m. Here the reaction was even more passive. Observations 
made at five minute intervals until 5:00 p.m. revealed no conflict 
whatever. At 6:00 p.m. the same observation was repeated and at 
8:00 a.m. the following day the situation remained the same. (Table 
2 .) 
Thus these later tests seemed entirely to confirm the earlier ones: 
the introduction of a “mass” of ten workers simultaneously pro- 
voked reactions not essentially different from those observed in the 
pair-tests on the one hand, and, on the other, in conspicuous con- 
trast to the situation when whole nests were introduced. This was 
true with moieties which had been maintained since isolation both 
on the same and on differing diets. 
Discussion 
Experiments testing compatibilities between workers from three 
moieties of an originally single nest population of Rhytidoponera 
metallica after mutual isolation for a period of two years under 
conditions identical except for diet on the one hand, and for another 
year between halves of one of these moieties isolated and main- 
tained under entirely identical conditions (including diet) led to 
some interesting conclusions. Pair-tests in fingerbowls indicated 
that some incompatibility, with accompanying suspicion or aggres- 
sion, could occur between individuals from isolated moieties main- 
tained on identical diets for a year, but it was infrequent. Both the 
frequency and vigor of aggression were somewhat greater when the 
tests were made between workers drawn from moieties isolated on 
differing diets but under otherwise identical environmental condi- 
tions. Thus it seemed possible that previous dietary history could 
have a minor role in mediating compatibility, but not an impor- 
tant — much less a decisive — one. Similar tests using ten-worker 
samples introduced between the moieties in all combinations yielded 
results essentially the same as the pair-tests, indicating that “mass 
