1981] 
Ward — Rhytidoponera impressa. I 
101 
Foraging and Food- Retrieval 
Members of the Rhytidoponera impressa group are partly 
predacious on other arthropods, but also scavenge for dead insects, 
seeds, animal feces, etc. Capture of live prey is achieved by a short 
lunge forward, coincindent with rapid closure of the outstretched 
mandibles. Prey thus captured are subdued by stinging. 
In most species, foraging occurs principally on the ground, 
among leaf litter and rotting logs. However, purpurea workers were 
frequently observed foraging on low foliage of understorey plants, 
as well as on the rainforest floor, in north Queensland. In Papua 
New Guinea this species nests (at least partly) arboreally, but limited 
observations (Wau; September, 1975) suggests that it tends to 
forage downward from the nest entrance. Urban and suburban 
populations of chalybaea, noted for their unusual nest sites (above), 
usually forage on the ground and on low vegetation, in damp tree- 
shaded situations. On one occasion chalybaea workers were ob- 
served foraging in a house in an urban residential area of Sydney. 
Foraging is not restricted to any particular time of the day or 
season, although activity decreases noticeably towards the middle of 
the day (and in the winter). Periods of clear warm weather after rain 
seem particularly conducive to high levels of foraging activity. 
Field observations indicate that workers are usually lone foragers, 
although occasionally several individuals co-operatively transport a 
large food item back to the nest. Sometimes this occurs close to the 
nest entrance, seemingly as a result of fortuitous encounters of a 
heavily-laden forager with other workers. In lab colonies of 
chalybaea, single workers struggling with a large prey item in a food 
arena were observed to make movements of the gaster suggesting 
stridulation. On the other hand, chemical recruitment to food 
sources does occur, although this behavior is rudimentary in 
comparison to the mass-recruitment patterns of some higher ants. It 
is readily demonstrated by placing large food baits (e.g. chunks of 
tuna fish or large insects) close to a nest. Workers which discover 
the food and return to the nest with a portion of the bait can be 
observed dragging the tips of their gasters along the ground, and 
subsequent outward-bound foragers follow the same path to the 
food (field observations on chalybaea and purpurea). Large pieces 
of the bait are retrieved co-operatively by several workers; smaller 
portions are carried by single foragers. 
