The effect of caste composition on wood consumption in cultures of Nasutitermes exitiosus (Hill) (Isoptera: Termitidae)

Abstract

Altering the proportions by weight of first-stage workers in groups of •large workers from 26 to 40 %, or of fourth-and fifth-stage reproductive nymphs in groups of mixed workers from 0 to 15%, did not affect wood consumption by laboratory cultures of Nasutitermes exitiosus (Hill). However, increasing the proportion of soldiers in groups of mixed workers from 0 to 15% decreased food consumption, which was very closely related to the weight of workers present. The presence of 7-5% of large workers near to ecdysis had no significant effect, but food consumption was depressed when the proportion reached 15%, apparently due to high mortality among the moulting workers. It is concluded that caste composition can be an important factor in laboratory tests of materials against termite attack and that, unlike soldiers or large workers near to ecdysis, first-stage workers and late-stage reproductive nymphs of N. exitiosus are substantially independent castes, at least in their feeding. IntroductionThe termites used in Australia for laboratory tests of the susceptibility of materials to termite attack are separated from their nests by a technique developed by Gay et al. (1955). An important part of this technique is ' papering', in which the broken nest material and termites are covered with sheets of stiff paper; termites transfer to the paper, permitting clean separation. We now know that some castes and stages of Nasutitermes exitiosus (Hill) transfer to the paper more readily than others, so that the caste composition of the papered termites differs significantly from that of the colony as a whole (McMahan & Watson, 1978); small soldiers and large workers of the second to fifth stages are more abundant in the papered samples, whereas larvae, first-stage small and large workers, and presoldiers are less so. Termites near to ecdysis are also under-represented.

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)

“…It is, however, very favourable for species of other termite genera from Australia, such as Mastotermes (Howick & Creffield, 1975), Porotermes (Lenz et al, 1982) and Nasutitermes (Howick & Creffield, 1979;Watson et al, 1978). However, the experiments were not aimed at establishing absolute differences between the two species for wood consumption and survival but at evaluating the pattern displayed by the two parameters under the influence of variations in group size and container volume, and the extent to which these patterns might differ between trie species.…”

“…in relation to different usage of provided space. (/)|Other factors with an impact on termite performance, and hitherto insufficiently tonsidered in bioassay procedures and standards, include species-specific requirements for amount of matrix in proportion to total container volume (Lenz & Williams, 1980), container shape (Lenz & Williams, 1980), group composition (Kny & Kuhne, 1982;Watson et al, 1978) and variability of results due to origin of termites, e.g. differences between colonies (Carter et al, 1972;Howick & Creffield, 1983;Lenz, 1983).…”

The effect of brown and white rot fungi on wood consumption and survival of Coptotermes lacteus (Froggatt) (Isoptera: Rhinotermitidae) in a laboratory bioassay

“…Type of matrix (BECKER and LENZ 1970;HOWICK and CREFFIELD 1975;LENZ, BECKER and GARCIA 1976;ESENTHER 1977a;HAVERTY in prep. ), volume and shape of containers and amount of matrix (HOWICK 1978;LENZ and WILLIAMS in press) and size and shape of timber specimens (OWICK 1975) can influence the performance of termite groups. Furthermore, the influence differs from s ecies to species.…”

Optimal Reproduction Strategies in Two Species of Mound-Building Termites

“…Young nymphs do not appear to feed themselves, as they lack the necessary gut microflora and their mandibles have little or no wear (Watson and Abbey, 1977;Lee and Wood, 1971;Watson et al, 1978). Furthermore, few nymphs are found in foraging sites away from the mound (Evans et al, 1998), suggesting that nymphs rely on workers for all or part of their food.…”