Nest 'moulting' in the ant Temnothorax albipennis

We showed how super- organisms, here ant colonies, modify their home according to their increasing or decreasing space requirements. The ontogeny of wall building by colonies of the ant Temnothorax albipennis involves discontinuous rebuilding events that are reminiscent of moulting in insects. Here for the first time we manipulated worker density by changing nest cavity size instead of worker number, thus avoiding accidentally shifting the balance of workers with different propensities for building tasks. Our results suggest for the first time that history influences wall building in ants when worker density decreases ( e. g. with colony diminution) as well as when it increases ( e. g. with colony growth) as shown by earlier work. Furthermore, we found that ants used a greater number of the larger building blocks ( big sand grains) both after cavity expansion and, more surprisingly, also after cavity contraction. The pattern of nest `moulting' we experimentally manipulated and analysed should provide insights into possible trade- offs between the various functions and structural properties of the nest that these animals may have to optimize. (C) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.