02342nas a2200265   4500008004100000245013400041210006900175260001200244300001200256490000700268520155900275653000801834653001301842653001501855653001601870653001201886653001501898653003001913653002501943653001501968100002101983700001802004700002002022856003402042       1999                        eng d00aDiscontinuous gas-exchange cycles in Scarabaeus dung beetles (Coleoptera : Scarabaeidae): Mass-scaling and temperature dependence0 aDiscontinuous gasexchange cycles in Scarabaeus dung beetles Cole  cSep-Oct  a555-5650 v723 aAlthough discontinuous gas exchange cycles (DGC) are known from many insects, the effects of body size and temperature on DGC have not been widely examined. Here, these effects are investigated in five Scarabaeus dung beetle species from mesic and xeric habitats. The investigation tests two hypotheses: that previous estimates of the scaling exponents for the DGC and its characteristics are more broadly applicable to insects, and that, in response to temperature, both DGC frequency and the quantity of CO2 emitted during the open (O) phase (O-phase emission volume) are modulated. Like previous workers, we find that (V) over dot (CO2) scaled as mass(0.968) and that O-phase emission volume scaled as mass(0.968) . However, temperature- associated increases in (V) over dot (CO2) (Q(10)'s of 2.19- 2.65) were modulated mostly by increases in DGC frequency since O-phase volumes remained constant across temperature. Flutter (F)-phase and O-phase durations were closely coupled to DGC duration, although the relationship between closed (C)-phase duration and DGC duration was less pronounced. We show that ventilation phase coefficients, previously considered a measure of the proportional duration of each phase of the DGC, calculated from the slopes of these relationships are a measure of change in phase duration with change in DGC duration and not a measure of the way in which total DGC duration is apportioned among phases. We suggest that proportions be used to estimate the contribution of each of the phases to the total duration of the DGC.10aant10aemission10aformicidae10ahymenoptera10ainsects10ametabolism10arespiratory transpiration10aventilatory patterns10awater-loss1 aDavis, A., L. V.1 aChown, S., L.1 aScholtz, C., H.  u<Go to ISI>://000084128100005