Including those body movements that might have masked abdominal pumping (mov) did not change this result considerably. Abdominal movements did also occur in

closed phases (see also Groenewald et al., 2012, Hetz et al., 1994 and Jõgar et al., 2011). The movements resembled abdominal respiration movements as observed in flutter phases (without additional leg or body movement), but were not accompanied by CO2 emission. With increasing AZD2281 clinical trial Ta the total duration of abdominal ventilation movements decreased exponentially ( Fig. 9), which coincided with the increase in cycle frequency reported in Section 3.2 ( Fig. 5). CO2 emission per cycle correlated positively with the duration of abdominal ventilation movements if calculated throughout all experiments (Fig. 10, F = 0.6211, P < 0.0001, N = 9). However, linear regression in 5 of 9 wasp individuals showed insignificant results, probably due to low variation of duration (compare inset in Fig. 10). Slopes of the individual wasps’ regression lines (F = 0.07872, P = 0.78715, N = 9) as well as y-intercepts

(F = 0.35149, P = 0.10295, N = 9) did not change significantly with Ta. At rest, many insect species show a particular respiration pattern of discontinuous gas exchange cycles (DGC; for review see Chown et al., 2006a, Lighton, 1996 and Sláma, 1988). The illustration of respiration patterns depends on flow rate, measurement chamber size (i.e. volume) and metabolic rate of the animal (Gray and Bradley, 2006, Lighton, 2008 and Terblanche and Chown, 2010). A large measurement chamber dilutes the animal’s CO2 trace, leading to a smoothed away signal at the selleck Smad inhibitor CO2 detector. Last but not least, the metabolic turnover of the tested animal is a crucial parameter (Gray and Bradley, 2003 and Moerbitz and Hetz, 2010). In resting yellow

jackets the CO2 emission varied in a wide range, from 5.6 μl g−1 min−1 at 7.7 °C to 101.3 μl g−1 min−1 at 40 °C (Käfer et al., 2012). With a measurement chamber size of 18 ml –as small as possible, but without impairing the animal’s natural movement – and a flow rate set to 150 ml min−1 the respiration patterns of Vespula sp. could be displayed throughout their entire viable temperature range. Typical DGCs consist of a closed phase with shut spiracles and no external gas exchange (Bridges et al., 1980) followed by a flutter phase with the spiracles opened in close succession, and the open spiracle phase (Hetz and Bradley, 2005 and Lighton, 1996). At the lowest experimental temperatures (Ta = 2.9 °C), DGC resembled an interburst–burst pattern similar to that described by Marais and Chown (2003) for Perisphaeria sp. cockroaches and Duncan and Dickman (2001) for Cerotalis sp. beetles. In Vespula sp. long interburst (closed) phases alternated with long open burst phases consisting of single peaks which sometimes tended to merge at the end of the open phase ( Fig. 1A), resembling to some degree “reversed” flutter phases.