Respiratory Rates of the Organ-Pipe Mud-Dauber Trypoxylon politum (Hymenoptera: Sphecoidea)1

Abstract

Oxygen consumption was determined at environmental temperatures throughout the life cycle of Trypoxylon politum Say. Feeding larvae consumed a mean of 90.63 µl O2/100 mg body weight/ hour (bw/h) and declined to 48.98 in the fully fed stage. Early and late cocoon spinning stages consumed 41.18 and 20.62 µl/O2/100 mg/h respectively. Oxygen consumption during diapause in prepupae, fell to 1.4 µl O2/100 mg bw/h and essentially remained at that level from summer to the following spring. Propupae consumed 4.67 µl O2/100 mg bw/h and the pupal stages exhibited a progressive increase in oxygen consumption during development to a maximum of 29.79 µl O2/ 100 mg bw/h immediately before adult emergence. The adults consumed a mean of 197.26 µl O2/ 100 mg bw/h. No difference in oxygen consumption due to sex of wasps was noted in pupal or adult stages. Log metabolism and metabolic rate vs. log body weight equations were calculated and the following slopes were determined: Larvae y = 283.6 X0.60 and y/x = 285.8 X−0.38; prepupae y = 8.04 X0.73 and y/x = 7.75 X−0.31; pupae y = 46.2 X0.17 and y/x 42.20.89; and adults y = 1060 X0.74 and y/x = 1060 X−0.26. The coefficients of determination (r2) indicate a good fit of the data to calculated slope values in larval stages, but decreased to near zero values in prepupae and pupal stages, and increased again in adults. We conclude that oxygen consumption in prepupal and pupal stages may be independent of body weight. The larval stage expends ca. 214 calories in respiratory energy reaching the prepupal stage (26.7% assimilated energy). The cost of overwintering maintenance is ca. 64 cal in the prepupal stage (8.0% assimilated energy), while the pupal stage requires ca. 166 cal (20.7% assimilated energy). These values compare favorably with calorimetrically determined energy budget for the wasp. The respiratory quotient determined for feeding larvae was 0.80 and all other stages had RQ's of 0.70. It appears that this wasp's metabolic rate is influenced by daily and general temperature fluctuations.