1981] 
Ward — Rhytidoponera impressa. I 
107 
which different nest sites are utilized, and these preferences are 
correlated with the availability of potential nest sites. The more 
tropical species ( impressa and purpurea) show a stronger preference 
for rotten logs, but occur at lower nest densities, than inhabitants of 
temperate and subtropical rainforest (< confusa and chalybaea). 
Where confusa and chalybaea occur sympatrically, they have 
significantly lower nest densities than allopatrically. 
Workers of the impressa group are generally lone-foraging 
predators and scavengers, but co-operative food retrieval and 
recruitment to food sources occur to a limited degree. The majority 
of food items are small arthropods: other ant species may be a 
significant component of the diet. Foraging usually occurs among 
leaf litter and logs on the ground but at least two species ( chalybaea 
and purpurea ) also forage on low foliage and tend homopterans. 
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