1981] 
Ward — Rhytidoponera impressa. I 
95 
while New Guinea records indicate a predilection for second-growth 
montane rainforest. 
Nest Site Preferences and Densities 
Members of the impressa group are found nesting mostly in 
rotten logs and under stones. Nests are multi-chambered, but not 
highly fragmented, seldom penetrating deeper than 15- 20cm into 
soil, or occupying more than lm length of rotting log. Nest 
entrances are cryptic, without conspicuous mounds of excavated 
material. 
Fallen epiphytes on the rainforest floor are occasionally utilized 
as nest sites by confusa and chalybaea. Duringthe present study no 
colonies were found in living epiphytes on trees, although there are 
single records of a colony-founding purpurea queen (Brown, 1954) 
and a mature purpurea colony (Wilson, 1958) from fern epiphytes 
on rainforest trees. 
Nest site records from the present study are summarized in Table 
2 which lists, for each species, the number of colonies collected from 
rotten logs, under stones, and in fallen epiphytes. Excluded from 
this table are a small number of single records from other nest sites. 
Thus confusa was also found nesting in a Banksia lignotuber, in a 
rotting bracket fungus, directly in the soil, and (twice) in an 
abandoned termite mound in rainforest. A chalybaea colony was 
located under the bark sheath of an Archontophoenix palm, and in 
urban areas this species occupied less orthodox nest sites (e.g. in and 
under rusting metal, under concrete slabs, and in crevices along a 
stone wall). Three purpurea colonies (two in north Queensland, one 
in Papua New Guinea) were observed nesting in cavities in the 
trunks of living rainforest trees, and in New Guinea this species may 
be primarily an arboreal nester (Wilson, 1958; records in ANIC). 
Table 2 shows that there is a clear trend towards greater 
specialization in the rotten log nest site in species of more tropical 
latitudes. The difference between confusa and chalybaea with 
respect to numbers of logs and stones utilized is highly significant 
(x? = 33.0, p < .001) and the difference between chalybaea and 
purpurea is also significant (x? = 4.4, p < .05). In contrast to all 
others, enigmatica (the localized species of wet sclerophyll gullies) 
appears to nest exclusively under stones. 
In 70 populations (from 63 localities, due to some sympatry) a 
tally was kept of the number of “potential” nest sites (rotten logs, 
