2B, e.g. at 7, 12 and 18 min). Probably, these are single peaks of a flutter phase, below the temporal resolution of our measurement setup and therefore forming a graduated slope. In our opinion these graduated slopes are flutter phases merging with the consecutive open phases ( Fig. 3, large triangles; Table 2, marked data). We suppose that this represents DGC on the verge of cyclic respiration. This resembles findings of Contreras and Bradley (2009) on R. prolixus. At temperatures higher than 36 °C, open phases of wasps occurred in such close succession that the peaks merged at the base and the CO2 signal never reached baseline levels. Their metabolic Cobimetinib supplier rate was so high that the produced

and emitted CO2 could not be entirely removed from

the measurement chamber before the next pulse was generated. The respiration pattern became entirely cyclic (compare Gray and Bradley, 2003). The wasps’ RMR increases exponentially with rising Ta (see Käfer et al., 2012)). They respond to the according demand of increased gas exchange with a likewise exponential increase in respiration frequency ( Fig. 5) but not with an increasing CO2 emission per respiration cycle ( Fig. 6). This was also reported for honeybees ( Kovac selleck chemicals et al., 2007) and fire ants ( Vogt and Appel, 2000). A comparison over flying and non-flying insect species reveals a positive correlation of respiration frequency and RMR ( Fig. 7, Table 1). In spite of a high variation in level as well as in slope of the single species data, Farnesyltransferase a trend is obvious in insects to increase CO2 emission with an increase in respiration frequency rather than in “depth of breath” or other measures. In the lower to medium temperature range (Ta = 10–27 °C), resting yellow jackets’ respiration

frequency did not differ much from that of honeybees (see Fig. 5). The increasing deviation of the curves above 27.5 °C could result from the exceptional steep increase in RMR in yellow jackets compared to honeybees (see Käfer et al., 2012). Regarding CO2 emission per respiration cycle, yellow jackets show a slight decrease with Ta similar to honeybees ( Kovac et al., 2007; Fig. 6). Because of virtually identical testing arrangements in Vespula sp. and Apis mellifera, a straight comparison of these two species is possible. At similar respiration frequencies ( Fig. 5), resting yellow jackets have a much higher energetic turnover (see Käfer et al., 2012) and emit CO2 on average in much higher amounts per cycle ( Fig. 6 and Fig. 7) than honeybees at similar ambient temperatures. Wasps seem to breathe more efficiently with respect to gas exchange volume per cycle than honeybees. This might base on anatomical (compare Snelling et al., 2011 on Locusta migratoria tracheae), physiological or behavioral differences between the two species.