310 
Psyche 
[December 
3. Individuals eclosed apart from a given community and returned 
to it after maturity, though “strangers” to the parent community 
as individuals, are characteristically accepted as compatible. This 
suggests that the qualities affecting compatibility are here in¬ 
nately determined (cf. Crozier and Dix, 1979) though further 
work with “alien” nurses remains to be done. 
All this suggests a genetic basis for the characteristics determining 
compatibility in R. metallica. The fact that the males of the species 
fly actively, and probably over some (though limited) distances, and 
mate, as we have demonstrated, with “calling” “laying workers” of 
neighboring colonies (Holldobler and Haskins, 1977; Haskins, 
1978), seems to fit this picture, suggesting an “interlaced” popula¬ 
tion, in which the frequencies of given matings between hypothetical 
colonies A and B diminish as some function of their spatial separa¬ 
tion. The degree to which compatibility patterns can be maintained 
in isolated populations suggests that several generations (one would 
guess, of course, thousands or more) may be required to achieve 
significant shifts of compatibility. 
Addendum* 
As a final test designed to distinguish genetic from environmental 
factors in colony—or population—discrimination in Rhytidopon- 
era metallica, a colony of this species, collected in the Blackall 
Range at Montville, Queensland, Australia on December 23, 1963, 
and maintained in the laboratory since that time in a stacked group 
of modified, earth-containing Lubbock-type artificial nests in a 
plastic arena was divided into two approximately equal moieties by 
placing half of the nest stack in each of two identical plastic arenas 
arranged side by side on the laboratory bench. Conditions of 
temperature, light, and humidity were virtually identical for the two 
groups. Each remained in nests familiar to it, and each continued to 
breed normally during subsequent months. The only difference in 
treatment was in feeding. One moiety was given fresh mealworms at 
the rate of twice a week. The other was supplied with fresh crickets 
at the same intervals. The moiety given mealworms was supplied 
with dilute sugar water as a carbohydrate source; the “cricket frac¬ 
tion” with dilute honey. 
'Addendum manuscript received by the editor September 22, 1980. 
