1KBIN-IRSNB, Département d'Entomologie, Rue Vautier 29, B-1000 Bruxelles, Belgium.
2ETHZ, Angewandte Entomologie, Clausiusstrasse 25, CH-8092 Zürich, Switzerland.
Sugars are the primary energy source for many ant species. Workers of Myrmica rubra were studied in a laboratory bio-assay with respect to their acceptance of sugar solutions as well as their capacity to survive on these solutions. Cohorts of workers received a 1 M solution of one of 13 sugars. The sugars tested included monosaccharides (fructose, glucose, galactose, mannose, rhamnose) as well as disaccharides (sucrose, trehalose, melibiose, lactose, maltose) and trisaccharides (melizitose, raffinose, erlose). Eleven of the 13 sugars increased M. rubra survival in comparison to a control group provided with water only. We found a high variation in the degree at which the individual sugars were accepted by the ants. This variation showed no apparent correlation with the nutritional suitability of the sugars. Thus, the nutritive value of a given sugar does not seem to be crucial in determining the behaviour of the workers. Furthermore, the data were analysed with respect to the monosaccharide composition of the sugars, in particular the occurrence of fructose, glucose and/or galactose. Our data suggest that M. rubra workers used fructose for short term energy supply, while glucose feeding covered energy supply over a more prolonged period, which might indicate its storage as glycogen. These data indicate that M. rubra can hydrolyse oligosaccharides by digestive enzymes. This aspect is under present study. Our overall results are in accordance with the fact that, in the field, a generalist ant species such as M. rubra exploits a broad range of sugar sources.