58 
Psyche 
[Vol. 92 
bees” that have been in contact with the queen during the previous 
30 min are sufficient to distribute the pheromonal signal effectively. 
Using the studies on honeybees as a model, first we investigated 
the rate at which radiolabel was transferred to virgin queens from 
a) food; b) the body surfaces of the mated queen, virgin queens, and 
workers; and c) small glass rods. The frequency of food transfer 
between workers and virgin queens in this experiment indicated that 
feeding might be involved in pheromone transfer. In a second exper- 
iment we examined whether feeding activity would increase the 
quantity of radioactive tracer transferred from the surface of the 
mother queen to the virgin queens. 
Materials and Methods 
Rate of transfer of food and surface materials. 
A total of 21 monogynous colonies of S. invicta were obtained 
from the field at College Station, Texas and their composition was 
standardized so that each consisted of about 20,000 workers, 40 cm3 
of worker brood, a moderately physogastric mated queen, and 400 
sexually mature virgin queens. These colonies were fed on a diet of 
insects and 50/50 (wt/wt) honey solution and kept at a temperature 
of 26° C. Colonies were housed in 2 artificial nests made of plaster of 
paris inside large plastic boxes. A bridge connected the nest box to a 
foraging arena (Mirenda and Vinson 1982). Colonies were fed con- 
tinuously before and during testing. 
To determine whether food transfer between workers and virgin 
queens occurred in substantially less than the 12 h required for the 
first virgins to dealate after orphaning, egg albumin and egg yolk 
powder were labeled with 125 Iodine (Sorensen and Vinson 1981) 
and offered singly to foragers along with the normal food supply. 
Beginning 15 min after the first forager re-entered the nest after 
leaving this food source, random samples of 10 virgin queens were 
taken every 15 min, alternating between the two nests for a total 
period of 2 h. Radiation was measured individually using a Searle 
1 195 gamma radiation counter. The threshold criterion for the pres- 
ence of radiolabel was any level of radiation above that of the 
background radiation plus two standard deviations. Disturbance to 
the colony was reduced by wearing face masks during sampling to 
eliminate exposure of the colony to breath C0 2 (Wilson 1971) and 
