104 
Psyche 
[Vol. 88 
Table 6. List of 1 9 food items returned to a single nest of Rhytidoponera croesus 
s.l. (Royal National Park, N.S.W., 26 January, 1976) over a three-hour observa- 
tion period. 
Hymenoptera: Formicidae: Paratrechina sp. (worker) 1 
" " Solenopsis sp. (worker) 1 
" " Chelaner sp. (worker) 1 
" " Myrmicinae (male alate) 1 
Hymenoptera: Pteromalidae (adult) 1 
Lepidoptera: adult microlepidopteran 1 
Lepidoptera: larvae 1 
Diptera: Nematocera (adults) 2 
Diptera: Brachycera (adults) 2 
Coleoptera: Chrysomelidae (adult) 1 
Homoptera: Coccoidea (nymph) 1 
Homoptera: Cicadellidae (nymph) 1 
Insect larva, unidentified 1 
Unidentified insect legs 2 
Acarina (small mite) 1 
Mammalian (?) excrement, with veg. matter and insect parts 1 
19 
single workers. Thirty-one (55%) of the 56 arthropod items were 
alive when retrieved from their captors (near the nest entrance). 
Some of the remaining items may have been killed or paralyzed 
during capture; others were clearly scavenged as dead material. 
It is of some interest to note that 19 (34%) of the 56 arthropod 
items consisted of other ant species (including alates). Some of these 
ants, particularly alates, may have been injured or dying when 
collected. On the other hand, predation on healthy, active worker 
ants was observed first-hand in the field: chalybaea workers from 
the Sydney University population were seen preying at the soil 
entrances of Pheidole nests, grabbing workers as they emerged. 
For comparison with another similar-sized, rainforest species of 
Rhytidoponera outside the impressa group, Table 6 lists the food 
items returned to a Rhytidoponera croesus nest over a three-hour 
observation period. The mean head widths for workers of croesus 
and chalybaea are 1.25 ± 0.03 s.d. (n=8) and 1.36 mm ± 0.08 s.d. 
(n=80), respectively. Although there is considerable similarity in 
food items taken by the two species as measured by ordinal 
taxonomic categories, an analysis of food size (Figure 3) reveals that 
the mean food item length of croesus (2.5 mm) is significantly less 
than that of chalybaea (3.5 mm) (t-test, p< .02). However, the food 
