An ant worker of the genus Diacamma foraging in the understorey of a lowland rain forest in Papua New Guinea. These ants belong to the species usually nesting in aerial soil in the canopy of primary forest trees (Photo and copyright: M. Janda, www.newguineants.org). Klimes, P., Idigel, C., Rimandai, M., Fayle, T.M., Janda, M., Weiblen, G.D. & Novotny, V. (2012) Why are there more arboreal ant species in primary than secondary forests? Journal of Animal Ecology, 81, 1103–1112.In a world where even documenting species declines in tropical systems is challenging enough, Klimes et al. raise the bar by addressing the deceptively simple, yet inherently complex, question of why species richness is lower in secondary forests. Using the first plot-scale inventory of arboreal ant nests, combined with an innovative rarefaction technique, they quantify the relative importance of a range of successional factors and highlight the contribution of beta diversity to the higher richness in primary forest.