@article {1451,
	title = {Discontinuous gas exchange and the significance of respiratory water loss in scarabaeinae beetles},
	journal = {The Journal of Experimental Biology},
	volume = {206},
	year = {2003},
	month = {Jul},
	pages = {3547-3556},
	abstract = {Respiratory 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. },
	keywords = {desiccation resistance, dung beetle, gas exchange, metabolic rate, scaling, Scarabaeus, water loss},
	author = {Chown, Steven L. and Davis, Adrian L. V.}
}
@article {1452,
	title = {Morphological correlates of flightlessness in southern African Scarabaeinae (Coleoptera: Scarabaeidae): testing a condition of the water-conservation hypothesis},
	journal = {Canadian Journal of Zoology},
	volume = {76},
	year = {1998},
	month = {Jan},
	pages = {1123-1133},
	abstract = {Flightlessness 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.},
	author = {Chown, Steven L. and Pistorius, Pierre and Scholtz, Clarke H.}
}
@article {2223,
	title = {Influence of dense stands of an exotic tree, Prosopis glandulosa Benson, on a savanna dung beetle (Coleoptera: Scarabaeinae) assemblage in southern Africa},
	journal = {Biological Conservation},
	volume = {78},
	year = {1996},
	pages = {305-311},
	keywords = {bush encroachment, invasive plant, mesquite, rare species, Scarabaeidae},
	author = {Steenkamp, H. E. and Chown, Steven L.}
}
