Tracing, Trophallaxis and Population Measurement of Colonies of Subterranean Termites (Isoptera) Using a Radioactive Tracer

Quantitative application of a radioactive tracer technique was used for field studies of the biology of subterranean termites. Heavy infestations of new plantations by colonies of Mastotermes darwiniensis (Froggatt) were traced to logs left unburnt after clearing and to invasion from nearby natural forest. The observations indicate that a colony consisted of one single nest containing eggs and larvae, one or more densely populated centers containing young workers, molting individuals, nymphs, mature workers and a relatively high proportion of soldiers. Many foraging sites contained mature workers and a small proportion of soldiers. Food transfer was shown to be very rapid and enabled estimates of population size to be made by isotope dilution analysis. Populations measured in colonies in mature natural forest are of the order of 7 × 105 insects and in new plantations 7 × 106 insects. Excretion rates of gut contents were determined. The basic bait is equally well eaten by Coptotermes acinaciformis (Froggatt) and Schedorhinotermes intermedius actuosus (Hill). While colony distribution could be traced in C. acinaciformis, no radioactive nests have yet been found with S. intermedius actuosus.