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[Vol. 92 
are distinct: carriers form a specialized group. For example, we 
observed 1 1 carriers make 40 transport trips from nest 59 to 60. The 
differences between carriers and recruits extended to physiological 
state, with carriers having relatively poorly-developed ovarioles 
(Table 5). 
Fukumoto and Abe (1983) found recruits to be indoor, and carri- 
ers to be outdoor, ants in the ponerine Diacamma rugosum, but the 
observation in Formica suggest that the carriers have an interme- 
diate position between the two groups (Rosengren, 1971). We there- 
fore attempted to demonstrate differences in the laboratory between 
carriers and recruits of Rhytidoponera sp. 12 in their preferences for 
darkened as against lit conditions. Ten ants from each group were 
individually placed into chambers made of two test tubes connected 
at their openings. One test tube was shaded using foil, and the other 
left uncovered. Each ant was allowed to select the dark or the light 
section of the chamber, and nine readings were made on each ant at 
half-hour intervals changing which end was shaded after each read- 
ing. The difference between the carriers and recruits is in the direc- 
tion expected although ranking the two series of ants does not quite 
reveal a statistically significant result (the value of the Mann- 
Whitney test statistic comparing the two distributions from Table 6 
is 72.5; whereas the value for the 5% level of a one-tailed test is 73, 
and for the 10% level it is 68). 
Hostility tests. 
Although ants from different nests often fight when they meet as 
foragers, the carrying phenomenon indicates that there must be 
considerable variation in the degree of hostility depending on the 
nests involved. We attempted to quantify the degree of hostility 
between different nests by moving ants between them. 
Trials in previous years using mutton baits had been highly suc- 
cessful in moving ants between nests with minimal disturbance. This 
method, however, proved hard to quantify and had to be aban- 
Table 5. Ovary development in carrier versus recruit ants collected during 
movements between colonies. 
Number of empty ovarioles 
0 
1 2 
3 
4 
5 
6 
Total 
carriers 
2 
1 1 
1 
1 
0 
9 
15 
recruits 
23 
1 3 
0 
0 
1 
4 
32 
