1979] Haskins & Haskins — Rhytidoponera metallica 311 
The separation and differential feeding was begun on November 
4, 1979, and continued until September 16, 1980. At that time indi¬ 
vidual pairs of workers from each moiety were tested for interac¬ 
tions in four inch fingerbowls, in the same manner as described in 
the main paper. Testing was carried out from 1:40 p.m. until 3:15 
p.m. on September 16, 1980. 
One hundred workers were tested, in fifty pairs of one from each 
moiety. Of these, 47 pairs, or 94 individuals, showed completely 
neutral (or “amicably interacting”) reactions. In two pairs there was 
a slight initial hostile reaction, but no attack. In only a single case 
one individual seized the other by the base of an antenna, maintain¬ 
ing the grip for a few seconds before spontaneously releasing it with 
no further aggression. 
As a control, workers from this same colony were tested on the 
same day against members of a colony of R. metallica collected at 
Sutherland, New South Wales, Australia, on January 12, 1968. 
These two colonies had been housed in similar Lubbock nests in 
arenas which had been maintained next to one another on the same 
laboratory bench for twelve years. Throughout this period, they had 
been fed identical diets: mealworms as a protein source, dilute sugar 
water as a source of carbohydrate. Thus diet, as well as all environ¬ 
mental conditions, had been maintained essentially identical for 
these two colonies over a twelve year period. 
Seventeen pairs, involving thirty-four workers, were tested in the 
same manner as in the preceding case. In fifteen of these there was 
an almost instantaneous and violently hostile reaction, the pairs 
quickly becoming “locked” in a mutually stinging posture which 
quickly results in fatalities to one or both participants unless they 
are forcibly separated. In one case the members of a pair showed no 
reaction; in a second pair there was a distinct “startle” reaction when 
the two individuals met, but no actual attack. 
The contrast between the behaviors of the members of a single 
genetically highly related population maintained on different diets 
in the one case and genetically separated populations maintained on 
identical diets in the other was very striking, and appeared to dem¬ 
onstrate quite unequivocally the predominant role of genetic factors 
in enabling colony (or “population”) discrimination in this species, 
as against the role of nutritional factors, further reinforcing the 
conclusions drawn from the evidence presented in the main portion 
of the paper. 
