Sheffield et al. 



JESO Volume 139, 2008 



Bloom 



2002 



FIGURE 7. Natural emergence of male and female Osmia lignaria from A) Nova Scotia and 

 B) Utah wintered in an unheated screened insectary, and the flowering phenology (percent 

 open bloom) of Mcintosh apples in 2002. 



Discussion 



Wintering success in insects is a complex symphony of internal physiological 

 adaptations and behaviour modifications prior to, during and following the winter. In 

 addition to these organism-level considerations, many ecological factors play significant 

 roles in dictating insect survival (Danks 1978, 1991; Leather et al. 1993). Surviving the 

 winter is therefore tied to several aspects of an insect's life history, and the most complete 

 understanding of its ability to overwinter successfully comes from taking all of these aspects 

 into consideration, as they do not necessarily work in isolation of one another (Danks 1978; 

 Leather et al. 1993). In addition, understanding the complexity of wintering mechanisms 

 which act on insect populations is critical to developing strategies for management which 

 involve, by necessity, a wintering period. 



Considering this, several factors may have contributed to the slight but significantly 

 higher survival of bees reared in Nova Scotia than those from Utah. The first and possibly 

 most important involved the comparative total length of the adult dormant period, in 

 particular the pre-wintering period. In Utah, O. lignaria is released for apple pollination 

 from late- April to mid-May, and adult activity usually ceases by mid-June (Torchio 1985; 

 Bosch and Kemp 2000, 2001). However, in Nova Scotia bees are released approximately 

 one month later as apple bloom typically occurs from late-May to mid-June (Fig. 7). In 

 terms of development, populations reared under ambient conditions in Utah reach the adult 

 wintering stage by August/September (Rust 1995; Bosch and Kemp 2000, 2001) which 



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