Overwintering management of Osmia Ugnaria 



JESO Volume 139, 2008 



Supercooling 



No significant differences in supercooling points were observed between sexes 

 within any of the treatment conditions, so sex-data within treatments were pooled. Significant 

 differences were found among the treatments (F = 15.62; df = 7; p < 0.001), so Tukey's 

 HSD test was used to separate means of the ranked data (Fig. 3). Early in the winter (i.e., 

 January), bees wintered outside (W-Out) from both locations of origin had significantly 

 lower supercooling points than their respective counter parts wintered inside (W-In) (Fig. 

 3). At this time, bees from Nova Scotia-Outside had slightly lower supercooling points 

 (mean = -19.4°C; n = 71; range = -10.1°C - -23.1°C) than those from Utah-Outside (mean 

 = -18.4°C; n = 45; range = -9.5°C - -22.7°C), but the differences were not significant. The 

 same trend was observed for bees wintered inside in the early winter: Nova Scotia (mean = 

 -17.4°C; n = 52; range = -6.8°C - -22.3°C); Utah (mean = -16.5°C; n = 47; range = -7.4°C 

 - -20.9°C). 



In the spring (i.e., March) outside (S-Out) treatment, bees from Utah (mean = 

 -18.3°C; n = 43; range = -8.3°C - -21.2°C) still had significantly lower supercooling points 

 than those inside (S-In) (mean = -16.5°C; n = 52; range = -10.7°C - -20.2°C), but no 

 differences were observed between the supercooling points of winter and spring bees in the 

 respective wintering site (Fig. 3). In the spring, the supercooling points of Nova Scotia bees 

 kept outside (mean = -17.0°C; n = 73; range = -9.6°C - -21.2°C) were lower but did not 

 differ significantly from those inside (mean = -15.6°C; n = 54; range = -5.3°C - -19.3°C). 

 Unlike the Utah population, bees from Nova Scotia (inside and outside) had significantly 

 reduced cold-hardiness in spring versus the winter (Fig. 3). Only within the S-Out treatment 

 did bees from both populations differ significantly. 



Weight Loss 



Significant differences were observed between the weights of bees from both 

 populations (F = 101 1.4; df = 3; p < 0.001), so means were separated using Tukey's HSD 

 test (p = 0.05). The pre-winter weights of bees from Utah were significantly greater than 

 bees reared in Nova Scotia (Fig. 4). Males from both populations were significantly lighter 

 than their respective females, but Nova Scotia females were significantly heavier than Utah 

 males (Fig. 4). 



Although significant differences were observed among all treatments (F = 4.55; 

 df = 15; p < 0.001), no significant differences in weight loss were observed among females 

 and males, or between wintering sites for bees reared in Nova Scotia (Figs. 5a and b). 

 Weight loss ranged between 1.2% - 2.1% total body wt in early winter, 1.8% - 2.6% by the 

 spring. Similar trends were observed in bees from Utah. Weight loss in the winter ranged 

 from 0.9% - 1.7%, overlapping the results from Nova Scotia bees. By the spring bees had 

 lost between 2.1% - 3.3% body weight (Figs. 5c and d). Utah females wintered inside lost 

 more weight by the spring than any other group (Tukey's HSD test; p = 0.05). In both 

 populations, early winter weight loss was slightly greater (though not significantly so) in 

 bees wintered outside than inside, while the reverse was observed in the spring (Fig. 5). 



Wintering Temperatures 



Temperatures inside the environmental chamber fluctuated slightly between 4°C 

 and 6°C throughout the experiment (Dec 2001 - May 2002) with a few notable exceptions 



9 



