Studies on feeding and trophallaxis in the subterranean termite Odontotermes formosanus using rubidium chloride

Differences in feeding and trophallaxis among castes of the fungus-cultivating higher subterranean termite Odontotermes formosanus Shiraki (Isoptera: Termitidae) were determined using rubidium (Rb) as a tracer. In the feeding study, workers and third instars fed directly on Rb-treated filter paper and acquired the highest levels of Rb content. Although fifth and sixth instars obtained the Rb content over the marked level, the feeding ability of the caste was very poor. However, soldiers did not feed on Rb-treated filter paper. In the trophallaxis study, worker, soldier, and fifth- and sixth-instar recipients paired with Rb-fed worker donors had a significantly higher Rb content than those paired with control donors. Results indicate that soldiers are completely dependent on workers for nutrition. Workers and fifth and sixth instars may obtain nutritional material from foraging workers. When third-instar recipients were paired with Rb-fed worker donors, they did not have a significantly higher Rb content than when they were paired with control donors, suggesting that the frequency of worker/third instar trophallaxis was very low. Transfer efficiency from the four trophallactic combinations ranged from 1.2 (worker donors to third-instar recipients) to 12.9% (worker donors to soldier recipients). Accordingly, nutritional material from foraging workers could be transferred to non-foraging workers, soldiers, and fifth and sixth instars by trophallaxis; however, third instars rarely obtain nutritional material from foraging workers, because they are capable of feeding within the nest.