1981] 
Ward — Rhytidoponera impressa. I 
97 
Table 3. Numbers of potential nest sites (pns) sampled and actual nests encoun- 
tered, for 70 impressa group populations. 
Species 
No. 
populations 
Logs 
Stones Epiphytes 
Total 
confusa 
37 
no. pns 
1838 
2984 
92 
4914 
no. nests 
227 
98 
8 
333 
nests/ pns 
.124 
.033 
.087 
.068 
chalybaea 
22 
no. pns 
1 164 
1136 
70 
2370 
no. nests 
141 
17 
1 
159 
nests/ pns 
.121 
.015 
.014 
.067 
impressa 
4 
no. pns 
260 
126 
7 
393 
no. nests 
8 
1 
0 
9 
nests/ pns 
.031 
.008 
.000 
.023 
purpurea 
5 
no. pns 
404 
109 
24 
537 
no. nests 
21 
0 
0 
21 
nests/ pns 
.052 
.000 
.000 
.039 
enigmatica 
2 
no. pns 
105 
561 
666 
no. nests 
0 
15 
15 
nests/ pns 
.000 
.027 
.027 
all species 
70 
no. pns 
3771 
4916 
193 
8880 
no. nests 
397 
131 
9 
537 
nests/ pns 
.105 
.270 
.047 
.060 
examining the proportion of potential nest sites which are occupied. 
(The desirable complementary data on absolute densities of poten- 
tial nest sites for different geographical regions and habitats are not 
available). Comparing the density figures (Table 3) for confusa and 
chalybaea, the former occupies a significantly greater proportion of 
stone nest sites than chalybaea (x? = 9.7, p < .01), but no differences 
exist in the proportion of suitable rotten logs occupied, and the 
overall nest densities (considering all potential nest sites) are the 
same for the two species. Nest densities are considerably lower for 
impressa, purpurea, and enigmatica. Rhytidoponera confusa and 
chalybaea utilize a significantly greater proportion of rotten logs 
than impressa and purpurea (contingency x\ p <.001, for all four 
comparisons), despite the greater importance of rotting logs as nest 
sites in the more northerly (tropical) species. This may be partly the 
result of greater competition for nest sites in the species-rich tropical 
rainforests. R. confusa and chalybaea are often common and 
dominant ants in temperate and subtropical rainforests, respec- 
tively, of New South Wales and southern Queensland where the 
