A DURATION CONSTANT FOR WORKER-TO-LARVA TROPHALLAXIS IN FIRE ANTS

The allocation of liquid food by workers to larvae, a central process in ant biology, could be regulated by the frequency of trophallaxis, i ts duration, or both. In 4th-instar fire ant larvae, the duration of t rophallaxis, bolus size, and the rate at which boluses were swallowed were all constant, indicating that the volume of food ingested during each worker-larva trophallaxis was both small and constant. Neither la rval size over a 20-fold volume range nor larval starvation had a sign ificant effect on duration of trophallaxis (mean=11 s, SD=2 s), bolus swallowing rate (mean=2/s, SD=0.5/s), or bolus volume (mean=0.0675 nl, SD=0.0002 nl, based on the assumption that the stomodaeum's epithelia l layer is not expandable). Larval body orientation and larval locatio n within the brood pile also had no effect on duration. Durations of t rophallaxis by workers of different sizes were similar. Durations of t rophallaxis for 1st-, 2nd-, and 3rd-instar worker larvae were also con stant but greater than that for 4th-instar worker larvae. Fourth-insta r minim larvae (from founding colonies) and 4th-instar worker larvae ( from mature colonies) were fed for the same duration by workers but fo r different durations by founding queens. Founding queens fed minim la rvae longer than they fed worker larvae. The durations of feedings to 4th-instar sexual larvae were more variable than those to worker larva e. Altogether, these findings indicated that 4th-instar worker larvae ingested a small, nearly constant volume of food (mean=1.50 nl, SD=0.0 05 nl) during each trophallactic event. Consequently, the long-term al location of liquid food by workers to these larvae is regulated by the frequency of trophallaxis. Several other ant species showed a similar brevity and constancy in the duration of worker-larva trophallaxis. T his brevity of worker-larva trophallaxis is in contrast to the duratio n of worker-worker trophallaxis. Although the duration of worker-larva trophallaxis appears to be determined by the worker, the data are not totally consistent with this interpretation.