Sheffield et al. 



JESO Volume 139, 2008 



Introduction 



The last few decades have witnessed many changes in the management of bees 

 (Hymenoptera: Apoidea) for the pollination of crops in North America. One of these changes 

 has involved a small but significant shift from reliance on one species, the ubiquitous honey 

 bee, Apis mellifera L., for most of our entomophilous pollination needs. The predictions 

 and warnings of potential problems likely to arise due to almost total reliance on honey 

 bees for crop pollination have been realized as evidenced by the large losses in the number 

 of colonies available for pollination (Kevan 2001; DeGrandi-Hoffman 2003) resulting in 

 recent native pollinator conservation initiatives and literature (Matheson et al. 1996; Stubbs 

 and Drummond 2001; Strickler and Cane 2003; Committee on the Status of Pollinators 

 in North America 2007). In response, interest in the development of non-Apis bees as 

 potential crop pollinators has increased, and several potentially useful species have been 

 investigated (Torchio 1990b, 2003; Bosch and Kemp 1999, 2000; Cane 2005). 



Some of the earliest research on non-Apis bees and their subsequent development 

 as crop pollinators started in the 1 940's in the USA (Torchio 1 990a). In addition to the need 

 to learn about basic bee biology and diversity, this early research was initiated because of the 

 realization that honey bees are poor pollinators of some crops and that several indigenous 

 species were more efficient crop pollinators (Bohart 1972). More recently, replacement 

 crop pollinators have been sought to fill gaps left by the increased demands on an ever 

 decreasing number of honey bee colonies, and these efforts have resulted in a growing 

 number of non- Apis bees being developed for management in North America (Parker et 

 al. 1987; Torchio 1990a; Richards 1993; Strickler and Cane 2003). However, the number 

 of bees currently managed does not approach 1% of the estimated 3000-4000 species in 

 America north of Mexico (Krombein et al. 1979). 



The main differences between managing honey bees and all other bee species 

 currently used for crop pollination in North America stem from differences in social 

 complexity and differing life histories. No other species of bee exhibits levels of social 

 behaviour as complex as that observed in the genus Apis (Michener 1 974, 2007). In America 

 north of Mexico, all indigenous bee species have a solitary stage in their life history, making 

 it the world's largest land area with no social species wintering as a colony. As such, 

 most temperate zone bee species have dormant periods corresponding to the winter season 

 (Stephen et al. 1969). 



Despite the fact that most bee species spend the largest proportion of their life 

 cycle in a non-reproductive/non-feeding stage often overlapping the winter months, little is 

 known about the behavioural and eco-physiological adaptations of bees leading up to and 

 during the winter in temperate zones (Sakagami et al. 1981; Hoshikawa et al. 1992; Rust 

 1995). For insects in general, properties of the wintering hibernacula such as moisture 

 levels, ground cover, nesting depth, the ground's slope and sun exposure levels are often 

 as important as the physiological and behavioural adaptations of the insect (i.e., cryo- 

 protectant synthesis, supercooling) for enhancing survival (Danks 1978, 1991; Leather et 

 al. 1993). Therefore, such factors are important and must be considered when developing 

 management techniques for solitary pollinators, as evidenced in the past by the works 

 of Krunic and Hinks (1972), Fairey et al. (1987), and more recently by Wilson and Abel 

 (1996), Bosch and Kemp (2000, 2003, 2004), Bosch et al. (2000), Kemp and Bosch (2005), 



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