|Kemp, William - Bill|
Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/26/2003
Publication Date: 1/2/2004
Citation: Kemp, W.P., Bosch, J., Dennis, B. 2004. Oxygen consumption during the life cycle of the prepupa-wintering bee Megachile rotundata (f.) and the adult-wintering bee Osmia lignaria say (Hymenoptera: Megachilidae. Annals of the Entomological Society of America.97(1):161-170. Interpretive Summary: Intensive agriculture, as practiced in much of North America, frequently presents large areas of a target crop requiring insect pollination to be in bloom simultaneously. The need for sufficient numbers of pollinators, ready at the appropriate time, to pollinate such areas has resulted in the development of artificial management protocols for the solitary bees M. rotundata and O. lignaria. Our results demonstrate large differences in the seasonal metabolic changes between these two species that have important implications to the continued improvement of artificial pre-wintering and wintering management regimes in the orchard pollinator O. lignaria. The apparent seasonal metabolic changes of adult O. lignaria observed in this study provide a physiological explanation to our previous observations of apparent fat body depletion and increased wintering mortality in O. lignaria exposed to elevated pre-wintering temperatures in California. The results of this study suggest that because O. lignaria exhibits proportionally greater oxygen consumption levels during the pre-wintering and wintering periods, it is important to minimize the exposure of O. lignaria to elevated temperatures once they have reached the adult stage in early autumn. In the continued development of these two species as commercial scale pollinators on an ever-increasing list of target crops, any similarities or contrasts observed between the "summer bee," M. rotundata, and the "spring bee," O. lignaria, while being of interest from a biological perspective, will likely have important implications in the continued development of sustainable population management protocols.
Technical Abstract: We studied the oxygen consumption of two megachilid bees (Hymenoptera: Megachilidae), Megachile rotundata (F.) and Osmia lignaria Say, at selected, biologically-relevant intervals throughout their respective life cycles. The U-shaped oxygen consumption curve and the static weights of wintering (non-feeding) prepupae that we observed for M. rotundata support previous arguments for a winter diapause similar to that observed in other Hymenoptera. For O. lignaria, which overwinters as an adult, we found increasing oxygen consumption temperature sensitivity and continuous weight loss throughout the wintering period. However, our observations on adult O. lignaria wintering requirements are consistent with the previously published results for overwintering M. rotundata prepupae, and reveal sharply increasing survival rates for both species when wintered for a minimum of three mo. In spite of the observed trends in temperature sensitivity of wintering O. lignaria, we interpret the greatly reduced survival in both M. rotundata and O. lignaria, as an indication that a critical biological process, diapause, is disrupted among individuals wintered for less than three mo. In the continued development of these two species as commercial scale pollinators on an ever-increasing list of target crops, any similarities or contrasts observed between the "summer bee," M. rotundata, and the "spring bee," O. lignaria, while being of interest from a biological perspective, will likely have important implications in the continued development of sustainable population management protocols.