Respiratory ventilation within one cycle consisted of one or several successions of single abdominal pumping movements. These successions were counted as single ventilatory events. The durations of these ventilatory events were determined, and related to the whole cycle as well as the cycle phases (open, closed or flutter). As we tested two species of vespine wasps, Vespula vulgaris and V. germanica, we had to analyze our data regarding the possibility of inter-species differences in respiration parameters. ANOVA revealed no influence of the tested wasp species on respiration cycle duration Gefitinib price (P = 0.5449, F-quotient = 0.39,

DF = 1) and CO2 release per cycle (P = 0.9239, F-quotient = 0.01, DF = 1; see Supplementary material, Table S1; data for the two species in Table S2). Therefore, species was not considered for the further analysis. Over the entire temperature range, spiracle control was functioning well for Vespula sp. At the lowest experimental temperatures (Ta = 2.9 °C) yellow jackets showed discontinuous gas exchange resembling an “interburst–burst” pattern similarly to that described by Marais and Chown (2003) for Perisphaeria sp. cockroaches. Interburst phases with LY294002 a minimum of 0.6 and a maximum of 81.73 min duration (mean: 11.86 ± 12.05 min) were followed by 0.42–14.57 min long burst phases (mean: 6.19 ± 4.91 min) consisting

of 1–5 initial higher peaks and several subsequent lower ones (see Fig. 1A). A flutter phase could not be observed at this Ta. Sporadic single CO2 spikes with similar peak height and duration as the initial peaks of the burst phases were counted as separate open phases. They caused the rather high SD in duration of GPX6 closed as well as open phases ( Fig. 3). With increasing Ta DGC appeared in a more common fashion with a closed phase followed by a distinct flutter phase and the main peak or open phase ( Fig. 2A). The open phase oscillations of the CO2 signal merged (but remained detectable), and flutter became visible ( Fig. 1B and C). At temperatures of 15–25 °C Vespula sp. showed typical DGC patterns ( Hetz and Bradley, 2005 and Lighton, 1996)

with closed, flutter and open phase ( Fig. 2B). Exceptional body movements, e.g. when the wasp lost and regained hold with a leg or flipped the wings ( Fig. 1B–D, arrows) were clearly distinguishable from the “normal” respiration pattern. At Ta = 26.2 °C the CO2 level inside the measurement chamber did not always reach zero between two respiration cycles. However, CO2 emission before the open phase resembled a flutter pattern consisting of merging single peaks. In certain individuals, residues of this particular pattern could be observed in some cycles as slight increases in the CO2 signal prior to the main respiratory peak even at Ta = 31.4 and 36.4 °C ( Fig. 2B, D; see large triangles in Fig. 3). At Ta > 31.4 °C all individuals showed cyclic respiration ( Fig. 2C). At the highest experimental temperatures (Ta = 39.7 and 42.