LAUSR

Simple Summary Insects have different strategies to adapt to environment change and parasites, but the supercooling response of pollinator populations under the biological stress has not been sufficiently investigated. This study assessed the supercooling traits of the solitary bee and its brood parasite. We discovered significant differences in the supercooling points were found between the solitary bee and its brood parasite in the same sex, and also between sexes of same species. The supercooling traits (supercooling points, fresh weight, and fat content) of the two species were significantly positively correlated. Our results suggest that the supercooling points of the solitary bee increase under the biological stress of its brood parasite at a certain level. Overall, the supercooling of pollinator populations varies regularly under brood parasitism pressure. Abstract (1) Background: Many insects have evolved different strategies to adapt to subzero temperatures and parasites, but the supercooling response of pollinator populations under the brood parasitism pressure has not been sufficiently investigated. (2) Methods: This study assessed the supercooling traits (supercooling points, fresh weight and fat content) of the solitary bee Osmia excavata Alfken and its brood parasite, Sapyga coma Yasumatsu & Sugihara. We measured 4035 samples (3025 O. excavata and 1010 S. coma, one individual as one sample) and discovered the supercooling traits relations between solitary bee and brood parasite. (3) Results: Significant differences in the supercooling points were found between O. excavata (females: −24.18 (−26.02~−20.07) vs. males: −23.21 (−25.15~−18.65) °C) and S. coma (females: −22.19 (−25.46~−18.38) vs. males: −20.65 (−23.85~−16.15) °C, p < 0.0001) in the same sex, and also between sexes of same species. The two species’ supercooling traits (supercooling points, fresh weight, and fat content) were significantly positively correlated. The supercooling points of the solitary bee varies regularly under brood parasitism pressure. (4) Conclusions: Our study indicates the supercooling traits relationships between a solitary bee and its brood parasite and suggests that the supercooling points of the solitary bee increase under the biological stress of its brood parasite in a certain level.