03096nas a2200229   4500008004100000245010200041210006900143260000800212300001400220490000800234520233100242653002702573653001602600653001702616653001902633653001202652653001502664653001502679100002202694700002502716856012502741       2003                        eng d00aDiscontinuous gas exchange and the significance of respiratory water loss in scarabaeinae beetles0 aDiscontinuous gas exchange and the significance of respiratory w  cJul  a3547-35560 v2063 aRespiratory water loss in insects is a controversial topic. Whilst earlier studies considered respiratory transpiration a significant component of overall water loss, to the extent that it was thought to be responsible not only for the evolution of discontinuous gas exchange cycles (DGCs) but also for variation in DGC patterns, later work repeatedly questioned its importance. In particular, investigations of the proportional contribution of respiratory transpiration to total water loss in species showing DGCs suggested that respiratory transpiration was unlikely to be important in these species. In turn, these studies have been criticized on analytical grounds. In this study we investigated variation in cuticular and respiratory water loss rates in five Scarabaeus dung beetle species, all of which show discontinuous gas exchange cycles, to ascertain the significance of respiratory water loss using modern analytical techniques. In particular, we determined whether there is variation in water loss rates amongst these beetles, whether both respiratory and cuticular water loss rates contribute significantly to variation in the former, and whether metabolic rate variation and variation in the duration of the DGC periods contribute significantly to variation in respiratory water loss rate. Total water loss rate varied such that species from arid areas had the lowest rates of water loss, and both cuticular and spiracular transpiration contributed significantly to variation in overall water loss rate. Moreover, variation in metabolic rate and in the duration of the DGC periods contributed significantly to variation in respiratory water loss rate. By contrast, examination of proportional water loss revealed little other than that it varies between 6.5% and 21%, depending on the species and the temperature at which it was examined. Cuticular water loss scaled as mass0.721, but did not differ from that expected from geometric considerations alone. By contrast, respiratory water loss scaled as mass0.531, suggesting that gas exchange takes place by diffusion and convection. Our results provide direct evidence that respiratory water loss forms a significant component of water balance, and that changes in both metabolic rate and DGC characteristics contribute to modulation of respiratory water loss. 10adesiccation resistance10adung beetle10agas exchange10ametabolic rate10ascaling10aScarabaeus10awater loss1 aChown, Steven, L.1 aDavis, Adrian, L. V.  uhttps://scarabnet.myspecies.info/discontinuous-gas-exchange-and-significance-respiratory-water-loss-scarabaeinae-beetles02006nas a2200157   4500008004100000245016500041210006900206260000800275300001400283490000700297520133800304100002201642700002201664700002401686856013801710       1998                        eng d00aMorphological correlates of flightlessness in southern African Scarabaeinae (Coleoptera: Scarabaeidae): testing a condition of the water-conservation hypothesis0 aMorphological correlates of flightlessness in southern African S  cJan  a1123-11330 v763 aFlightlessness in desert beetles is thought to have evolved either as a response to decreased environmental heterogeneity or directly to reduce water loss. The water-conservation hypothesis rests on three conditions: that spiracular transpiration is greater than cuticular transpiration; that cuticular transpiration rates are lower in desert species; and that changes in body form associated with flightlessness lead to an overall reduction in water loss rates. The extreme form of the morphological-convergence condition suggests that this change in body shape should be most pronounced in desert-dwelling taxa. The morphological-convergence condition was examined using a morphometric analysis of body shape in flying and nonflying dung beetle species from two southern African tribes occurring in arid and mesic habitats. Although the Canthonini have a more rounded body than the Scarabaeini, flightless species in both tribes have a more rounded body than the flying ones, except at the smallest body sizes. This rounding is more pronounced in flightless, desert-dwelling Scarabaeini than in flightless species from more mesic habitats. All three conditions required by the water-conservation hypothesis are met in various beetle taxa, but the hypothesis and its conditions have yet to be tested on a single, monophyletic taxon.1 aChown, Steven, L.1 aPistorius, Pierre1 aScholtz, Clarke, H.  uhttps://scarabnet.myspecies.info/morphological-correlates-flightlessness-southern-african-scarabaeinae-coleoptera-scarabaeidae-testin00740nas a2200181   4500008004100000245015900041210006900200300001200269490000700281653002200288653001900310653001300329653001700342653001700359100002200376700002200398856013800420       1996                        eng d00aInfluence of dense stands of an exotic tree, Prosopis glandulosa Benson, on a savanna dung beetle (Coleoptera: Scarabaeinae) assemblage in southern Africa0 aInfluence of dense stands of an exotic tree Prosopis glandulosa   a305-3110 v7810abush encroachment10ainvasive plant10amesquite10arare species10aScarabaeidae1 aSteenkamp, H., E.1 aChown, Steven, L.  uhttps://scarabnet.myspecies.info/influence-dense-stands-exotic-tree-prosopis-glandulosa-benson-savanna-dung-beetle-coleoptera-scaraba