Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2000
Publication Date: 8/1/2000
Citation: Kemp, W.P., Bosch Gras, J. 2000. Development and emergence of the alfalfa pollinator, megachile rotundata (hymenoptera: megachilidae). Annals of the Entomological Society of America. Interpretive Summary: The alfalfa leafcutting bee is used as a pollinator for alfalfa seed production in most of the U.S. Pacific Northwest states. There are currently a number of bee production problems that alfalfa seed producers have asked us to address. Answers to the questions posed require a fundamental understanding of alfalfa leafcutting bee development and survival when reared under different temperature regimes. This manuscript reports on bee development and survival from the egg stage through adult. This information will be compared to results obtained under field-scale commercial seed production conditions, throughout the Pacific Northwest, to develop recommendations for producers which will increase bee survival and reproduction, thereby improving on-farm profitability.
Technical Abstract: Megachile rotundata (Fabricius), a gregarious, cavity-nesting, leaf- cutting bee, is used throughout North America for the pollination of alfalfa, Medicago sativa L., seed crops. We examined the influence of various temperature regimes on development, survival, emergence, and longevity in both non-diapausing and diapausing forms of this species. In general, development rates increased with increasing constant temperatures used in this study (18, 22, 26, and 29 C), but the 26 and 29 C treatments were clearly superior as rearing temperatures for immatures. In diapausing individuals, a variable temperature treatment 14:27 C (8:16h daily cycle, mean 22 C) reduced the length of prepupal and pupal development stages following incubation in the early summer when compared with individuals reared under the constant 22 C treatment. We discuss the importance of differing temperature regimes on M. rotundata development, survival, and longevity over the entire life cycle. We also discuss the importance of making a connection between immature developmental and sufficient wintering conditions to post- diapause development, a topic which has received much more attention in the literature.