NECTAR FEEDING BY THE ANT CAMPONOTUS MUS - INTAKE RATE AND CROP FILLING AS A FUNCTION OF SUCROSE CONCENTRATION

In independent assays, workers of the ant Camponotus mus were conditio ned to visit an arena where they found a large drop of sucrose solutio n of different concentrations, from 5 to 70% weight on weight (w/w). S ingle ants were allowed to collect the sucrose solution ad libitum, an d feeding time, feeding interruptions, crop load, and intake rates wer e recorded. Feeding time increased exponentially with sucrose concentr ation, and this relationship was quantitatively described by the incre ase in viscosity with concentration corresponding to pure sucrose solu tions. Ants collecting dilute solutions (5 to 15% w/w) returned to the nest with partial crop loads. Crop filling increased with increasing sucrose concentration, and reached a maximum at 42.6% w/w. Workers col lecting highly concentrated solutions (70% w/w) also returned to the n est with a partially-filled crop, as observed for dilute solutions. Ne ctar intake rate was observed to increase with increasing sucrose conc entration in the range 5 to 30% sucrose. It reached a maximum at 30.8% , and declined with increasing sucrose concentration. Results suggest that both sucrose concentration and viscosity of the ingested solution modulate feeding mechanics as well as the worker's decision about the load size to be collected before leaving the source. (C) 1998 Elsevie r Science Ltd. All rights reserved.