1972] 
McCluskey Brown — Paraponera 
343 
in DD, here through two different types of assay. Internal timing 
is implied in LD by the rise before dawn or dusk signals (Fig. 4 
and 5B) . 
At the same time a group of 10 workers in one two-chambered 
nest were observed by eye. Each chamber was a clear plastic box 
about 10 cm in diameter and depth. One chamber was darkened 
and had water and sugar water provided ; the other served as an 
arena, dry and fully exposed to the light cycle. The activity level 
was high during the light period, and low during the dark period 
(Fig. 4 and 5D). The simultaneously-observed rhythm of number 
out in the arena was similar in form, though less prominent (Fig. 
5D). There was no evidence of persistence of activity rhythm 
(Fig. 4) or arena rhythm (not shown) in DD, though the data are 
too brief to be conclusive. 
When either capacitance counter assembly became available, a 
single worker was placed in it for counts. This was done for three 
different individuals. There were problems, such as the ant pulling 
out the cotton from one of the tubes and flooding the chamber. Fig. 
5C combines all the records that were obtained when the conditions 
were tolerably satisfactory. There appear to be peaks of activity 
during the first and last parts of the light period. 
Discussion 
It should be stressed that conclusions apply only to the particular 
specimens studied, since replication consisted mainly of different 
days for the same ant or group, rather than of separate ants or groups. 
In the field in January the ants of this colony were crepuscular 
and nocturnal in their appearance outside the nest (Fig. 1). In 
room conditions the workers appeared out in the arena especially 
around laboratory dawn and dusk, and their activity level also peaked 
strikingly at these two times (Fig. 2). In LD there were moderate 
tunnel activity peaks at the beginning and end of the light period, 
but, surprisingly, number out in the arena and especially activity 
index were both much higher through the light period than the dark 
(Fig. 5D). Why this contrast with the field, where the ants were 
not seen out during the day? 
Among other possibilities, several suggest themselves. The ants 
were in extremely artificial nests — no dirt, no queen, etc. There 
was less of a temperature cycle in the laboratory than outside, and 
the light was dimmer than even in the forest conditions. Further, 
the gradual dawn and dusk of the field might be important in phas- 
ing the activity, as it is in certain mammals (Kavanau, 1967). 
