00717nas a2200193   4500008004100000245010500041210006900146300001400215490000800229653001100237653002300248653003700271653001700308653001300325653002200338100002200360700002400382856011700406       2003                        eng d00aThe role of the subelytral spiracles in respiration in the flightless dung beetle Circellium bacchus0 arole of the subelytral spiracles in respiration in the flightles  a1309-13180 v20610abeetle10aCircellium bacchus10adiscontinuous gas exchange cycle10aScarabaeidae10aspiracle10asubelytral cavity1 aByrne, Marcus, J.1 aDuncan, Frances, D.  uhttps://scarabnet.myspecies.info/role-subelytral-spiracles-respiration-flightless-dung-beetle-circellium-bacchus03096nas 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-beetles02203nas a2200253   4500008004100000245009800041210006900139260000800208300001400216490000800230520139100238653001601629653001401645653001601659653002501675653001301700653001201713653002701725653001401752100001701766700002101783700002401804856012101828       2003                        eng d00aTwilight orientation to polarised light in the crepuscular dung beetle Scarabaeus zambesianus0 aTwilight orientation to polarised light in the crepuscular dung   cFeb  a1535-15430 v2063 aThe polarisation pattern of skylight offers many arthropods a reference for visual compass orientation. The dung beetle Scarabaeus zambesianusstarts foraging at around sunset. After locating a source of fresh droppings, it forms a ball of dung and rolls it off at high speed to escape competition at and around the dung pile. Using behavioural experiments in the field and in the laboratory, we show that the beetle is able to roll along a straight path by using the polarised light pattern of evening skylight. The receptors used to detect this skylight cue can be found in the ommatidia of the dorsal rim area of the eye, whose structures differ from the regular ommatidia in the rest of the eye. The dorsal rim ommatidia are characterised by rhabdoms with microvilli oriented at only two orthogonal orientations. Together with the finding that the receptors do not twist along the length of the rhabdom, this indicates that the photoreceptors of the dorsal rim area are polarisation sensitive. Large rhabdoms, a reflecting tracheal sheath and a lack of screening pigments make this area of the eye well adapted for polarised light detection at low light levels. The fan-shaped arrangement of receptors over the dorsal rim area was previously believed to be an adaptation to polarised light analysis, but here we argue that it is simply a consequence of the way that the eye is built.10adung beetle10aommatidia10aorientation10apolarisation pattern10areceptor10arhabdom10aScarabaeus zambesianus10askylight.1 aDacke, Marie1 aNordstrom, Peter1 aScholtz, Clarke, H.  uhttps://scarabnet.myspecies.info/twilight-orientation-polarised-light-crepuscular-dung-beetle-scarabaeus-zambesianus02075nas a2200217   4500008004100000245005000041210005000091300001400141490000800155520142500163653002301588653003701611653001601648653001601664653001701680653001301697653002301710100002401733700002201757856007801779       2002                        eng d00aRespiratory airflow in a wingless dung beetle0 aRespiratory airflow in a wingless dung beetle  a2489-24970 v2053 aThe sealed subelytral cavity of many flightless beetle species is widely acknowledged to be an adaptation to water saving in arid-habitat species. However, this hypothesis relies on the acceptance of two largely untested assumptions: (i) that the movement of respiratory gases is unidirectional from anterior to posterior and (ii) that the coordinated action of the spiracles directs this flow. We tested these assumptions by simultaneously measuring CO2 and O2 exchange at the anterior mesothorax, independently of gas exchange in the posterior body, which included the subelytral cavity, of a large apterous beetle, Circellium bacchus. Flow-through respirometry revealed a marked discontinuous gas-exchange cycle (DGC) pattern from the anterior half of the body. Very little CO2was released from the posterior body, where the DGC was not apparent. Labelled air was shown to flow forwards from the posterior to the anterior body. Individual sampling from the mesothoracic spiracles revealed that the right mesothoracic spiracle, lying outside the elytral cavity, is the primary route for respiratory gas exchange in C. bacchusat rest. This discovery necessitates a reassessment of the currently assumed role of the subelytral cavity in water conservation and is, to our knowledge, the first demonstration of forward airflow associated with the unilateral use of a single thoracic spiracle for respiration in an insect. 10aCircellium bacchus10adiscontinuous gas exchange cycle10adung beetle10arespiration10aScarabaeidae10aspiracle10asubelytral cavity.1 aDuncan, Frances, D.1 aByrne, Marcus, J.  uhttps://scarabnet.myspecies.info/respiratory-airflow-wingless-dung-beetle01923nas a2200217   4500008004100000245005900041210005900100260000900159300001400168490000800182520126500190653003001455653002201485653001201507653001701519653002501536100002001561700001901581700001601600856008901616       1995                        eng d00aUltrasound acoustic startle response in scarab beetles0 aUltrasound acoustic startle response in scarab beetles  cJuly  a2593-25980 v1983 aWe discovered an auditory sense in a night-flying scarab beetle, Euetheola humilis, the first scarab to be shown to hear airborne sounds. In the field, beetles were captured beneath speakers broadcasting ultrasound that simulated bat echolocation pulses. Apparently, the beetles took evasive action from a potential bat predator and flew into the traps. Using another behavioral assay in laboratory studies, the beetles were sensitive to frequencies ranging from 20 to 70kHz at levels between 60 and 70dB SPL. One component of the behavioral response, a head roll, was graded with stimulus intensity, and the number of potentials in electromyographic recordings from muscles involved in the roll increased as stimulus intensity increased. The response latency was about 40ms at threshold, decreasing to about 30ms at 20dB above threshold. The beetle’s short response latency is ideally suited for predator avoidance behavior and the frequency tuning of the response suggests that it could function in evasion from insectivorous bats. The beetle’s acoustic sensitivity is remarkably similar to that of other night- flying insects showing ultrasound-induced startle and it should provide these scarab beetles with a similar advance warning of predation risk.10aacoustic startle response10aEuetheola humilis10ahearing10aScarabaeidae10aultrasound avoidance1 aForrest, T., G.1 aFarris, H., E.1 aHoy, R., R.  uhttps://scarabnet.myspecies.info/ultrasound-acoustic-startle-response-scarab-beetles