Polyethism in food processing and social organisation in the nest of Macrotermes bellicosus (Isoptera, Termitidae)

Abstract

Polyethism in food processing and the social organisation in the nests of Macrotermes bellicosus field colonies were investigated by characterising the gut contents and the labial glands (dry weight and protein content) of workers. Workers from three different nest areas i.e. foraging sites, the fungus comb and the queen cell, were examined. Two different feeding groups were distinguished by the colour of the workers' abdomen. Dark-brown was noted in the majority of workers. They fed on fungus comb (secondary food). Workers with a reddish-brown abdomen fed on the collected plant litter (primary food). A clear caste polyethism was found in the selection of food intake. The ratio of major workers to minor workers having primary food in their gut was significantly higher in both the queen cell and the fungus comb. The fungus comb is built up of primary faeces hence major workers dominated in fungus comb construction. This indicates that food processing in the colony is predominantly carried out by major workers. The two different feeding groups were also found in the queen cell. Workers with secondary food in the gut had labial glands with a significantly higher dry weight and absolute protein content than workers that consume primary food. The existence of two different kinds of nurses in the queen cell is discussed: workers which feed nodule material and those which feed saliva to the reproductives. In addition, labial glands of both major and minor workers from the queen cell had a higher absolute content of proteins than labial glands of workers from foraging sites. In M. bellicosus the physiological difference in gut contents and labial glands seems to depend on age and to be task-related.