1981] 
Ward — Rhytidoponera impressa. I 
91 
dispersal, and mating behavior were also made. In addition, field 
observations and collections of related Rhytidoponera species from 
Australia, New Guinea, and New Caledonia provided some com- 
parative data. 
Results 
Habitat Preferences 
The known members of the Rhytidoponera impressa group and 
their respective distributions are as follows (Ward, 1980): chalybaea 
Emery (= cyrus Forel), New South Wales, southern Queensland, 
New Zealand (introduced); confusa Ward, Victoria, New South 
Wales, southern Queensland; enigmatica Ward, New South Wales; 
impressa Mayr, Queensland; and purpurea Emery (= splendida 
Forel), northern Queensland, New Guinea. 
Most species in the impressa group occupy a considerable range 
of latitude, altitude and forest types; and all species show partial 
sympatry with at least one other species (Table 1). In this context, a 
sympatric association is defined as the occurrence of two (or more) 
species within the dispersal range of their alates. In all cases of 
sympatry, non-conspecific nests were located within several hun- 
dred meters of one another, and in most instances within 50 meters. 
Despite the overlap between species, differences in habitat prefer- 
ences are apparent. 
R. confusa is essentially a species of wet sclerophyll forest and 
temperate rainforest. In Victoria and southern New South Wales it 
is principally confined to lowland wet sclerophyll, and does not 
occupy cool temperate rainforest of the type dominated by such 
trees as Nothofagus, Quintinia, and/or Atherosperma. At the 
northern limit of its range, confusa is restricted to temperate and 
subtropical rainforest at moderate to high elevations. Thus, there is 
an inverse relationship between elevation and latitude (Figure 1), 
and the regression of altitude on latitude indicates an average shift 
of about 70m per degree latitude. 
In contrast to confusa, chalybaea is common in subtropical 
rainforest of northern New South Wales and southern Queensland 
(where confusa is rare or absent). At the southern limit of its 
distribution, chalybaea is confined to disturbed lowland habitats. 
Thus, in the Sydney region, it occurs commonly in well-watered 
parks and gardens, and only penetrates wet sclerophyll and 
