90 
Psyche 
[Vol. 88 
Methods 
Data were gathered during a survey of the Rhytidoponera 
impressa group from approximately 100 mesic forest sites in eastern 
Australia and New Guinea. A detailed tabulation of these collection 
sites is given in Ward (1978). Field work was carried out from 
October, 1974 to October, 1978, with a few additional collections in 
May-July, 1980. Voucher specimens from these collections have 
been deposited in the Australian National Insect Collection (ANIC), 
CSIRO, Canberra. 
In rainforest and wet sclerophyll forest the collection procedure 
was as follows: colonies of the impressa group were sought by 
examining all rotting logs, loose stones and other potential nest sites 
which were encountered during a more or less random (i.e. 
undirected) walk through a tract of suitable forest. In most localities 
a tally was kept of the number of “potential nest sites” (logs and 
stones) sampled. The “rotting log” count was confined to moist 
rotten logs in middle to late stages of decay, with numerous 
preformed cavities (corresponding roughly to the “zorapteran” and 
“passalid” stages of Wilson, 1959), since field observations showed 
that recently fallen or dessicated logs were rarely inhabited. If a 
single large log was dissected in two places more than 1 meter apart 
it was counted as two potential nest sites. Records from rotting logs 
include a few instances where ants also nested in soil below the log. 
Stones ranging in areal size from about 100 to 1500 cm 2 were 
recorded as potential nest sites if they rested completely on the 
ground and could be easily overturned. Fallen epiphytic fern masses 
on the rainforest floor were also considered potential nest sites and 
were examined and counted in areas where they occurred. Almost 
invariably, a single colony occupied only one nest site, so the terms 
“colony” and “nest” are used in equivalently in this paper. 
When an impressa group colony was located, an attempt was 
usually made to collect the entire colony contents, i.e. all workers, 
reproductives, and brood. This entailed considerable excavation of 
rotting wood and/or soil. Where only colony fragments were 
believed to be collected, this was noted. 
Collected colonies were returned to the lab and their contents 
enumerated. A few were maintained in modified Janet or Lubbock 
nests. The majority were frozen for electrophoresis. 
Field observations of foraging behavior, colony movement, alate 
