Implications for comparability of laboratory experiments revealed in studies on the effects of population density on vigour in Coptotermes lacteus (Froggatt) and Nasutitermes exitiosus (Hill) (Isoptera: Rhinotermitidae & Termitidae)

Abstract

The vigour, i.e. survival and wood consumption, of groups of Coptotermes lacteus (Frogg.) and Nasutitermes exitiosus (Hill) was measured when termites were kept at different population densities by changing group size and/or volume of the holding container. A characteristic pattern emerged for subterranean termite species. At low population densities (<0-01 g termites/ml), performance improved with an increase in group size; at higher densities, it tended to decline. The impact of altering group size and container volume on termite vigour was most pronounced at low population densities; at higher population densities, performance tended to be more stable but declined markedly when termites became overcrowded. In most jar-type experiments on termites, especially those conducted in Europe and the USA, small groups of termites are housed in disproportionately large jars, resulting in very low, sub-optimal population densities. Suggestions are made for improvement in experimental design that would lead to an enhancement of the comparability of results from different laboratories.

Effect of group size and caste ratio on individual survivorship and social immunity in a subterranean termite

“…We do find a strong effect of social group size on survivorship (Table 1), but this effect was not related to resistance. Termites living in larger groups live significantly longer, confirming that for many species of termites group size is positively correlated with survivorship (Lenz and Barrett 1984;Rosengaus et al 1998b). We do not rule out the possibility of a density effect on resistance, and future studies could increase power to detect it over previous studies with larger sample sizes and increased ranges in size classes, perhaps spanning three or more orders of magnitude.…”

Evaluation of an entomopathogenic fungus,Paecilomyces fumosoroseus(Wize) Brown and Smith (Deuteromycota: Hyphomycetes) obtained from Formosan subterranean termites (Isop., Rhinotermitidae)

“…In this study, C. formosanus treated with control solution and kept alone died more than twice as fast as those kept in small groups, and C. formosanus kept in large groups (1000–2000) with colony material, such as in the bottles received at EBCL, could live 6 months or longer. That group size is positively correlated with survivorship is well known ( Lenz and Barrett , 1984; Rosengaus et al, 1998b), particularly when termites are exposed to fungal pathogens ( Boucias et al, 1996; Rosengaus et al, 1998b). In our experiments, the relationship between fungal dose and median survivorship was weaker among grouped termites than among termites kept alone, but among grouped termites Pfu02031 reduced median survivorship significantly more than did M. anisopliae .…”

Factors Affecting Performance of Soil Termiticides

“…Jones (1990) found that while large groups of termites tunneled more than small groups in soils treated with chlordane, chlorpyrifos, or permethrin, group size had different effects on mortality in different soil treatments. Several experiments have demonstrated correlations between termite survival rates and population density (Lenz et al, 1984;Lenz, 2009;Santos et al, 2004). At population densities below 0.1 g termites / ml, Lenz et al (1984) found that, in the absence of termiticide treatment, survival of Coptotermes lacteus (Froggatt) and Nasutitermes exitiosus (Hill) increased with population density.…”

“…Several experiments have demonstrated correlations between termite survival rates and population density (Lenz et al, 1984;Lenz, 2009;Santos et al, 2004). At population densities below 0.1 g termites / ml, Lenz et al (1984) found that, in the absence of termiticide treatment, survival of Coptotermes lacteus (Froggatt) and Nasutitermes exitiosus (Hill) increased with population density. Susceptibility differences occur among termite species and colonies.…”