Responses of the bed bug,Cimex lectularius,to temperature extremes and dehydration: levels of tolerance,rapid cold hardening and expression of heat shock proteins

This study of the bed bug, Cimex lectularius, examines tolerance of adult females to extremes in temperature and loss of body water. Although the supercooling point (SCP) of the bed bugs was approximately −20°C, all were killed by a direct 1 h exposure to −16°C. Thus, this species cannot tolerate freezing and is killed at temperatures well above its SCP. Neither cold acclimation at 4°C for 2 weeks nor dehydration (15% loss of water content) enhanced cold tolerance. However, bed bugs have the capacity for rapid cold hardening, i.e. a 1‐h exposure to 0°C improved their subsequent tolerance of −14 and −16°C. In response to heat stress, fewer than 20% of the bugs survived a 1‐h exposure to 46°C, and nearly all were killed at 48°C. Dehydration, heat acclimation at 30°C for 2 weeks and rapid heat hardening at 37°C for 1 h all failed to improve heat tolerance. Expression of the mRNAs encoding two heat shock proteins (Hsps), Hsp70 and Hsp90, was elevated in response to heat stress, cold stress and during dehydration and rehydration. The response of Hsp90 was more pronounced than that of Hsp70 during dehydration and rehydration. Our results define the tolerance limits for bed bugs to these commonly encountered stresses of temperature and low humidity and indicate a role for Hsps in responding to these stresses.     

MOTIVATIONS FOR PRODUCT CONSUMPTION: APPLICATION OF A PROBABILISTIC MODEL TO ADOLESCENT SMOKING

This paper describes a method that can be used to investigate consumers' reported reasons for using a particular product. This method is applied to ratings of degree of agreement with statements about reasons for product use. The method is illustrated using data on self-reported reasons for smoking among adolescents. The approach used is based on a probabilistic model of similarity (Ennis et al. 1988) and provides a display of the density of respondents' individual motivations concurrent with their perceptions of the statements. Factor analysis and its derived factor scores provide complementary information which is used to understand the interdependence of smoking motivations with the age of respondents and their degree of smoking. The probabilistic similarity model has many applications in studying consumer motivations such as those involved in the consumption of particular food and personal care products.