A Combination Method of CO 2 -Narcosis and Cold Treatment for Breaking Diapause of Bombus ignitus and Bombus terrestris Bumblebee Queens

Abstract

Int. J. Indust. Entomol. Vol. 28, No. (2), pp. 58-65 (2014) 58 59 ing carbon dioxide (a 30-min narcosis treatment repeated twice) would start laying eggs within a week. However, this method produced many side effects. Pormeroy and Plowright (1979) found that this treatment induced the ejection of larvae by bumblebee workers in narcotized colonies. Röseler (1985) reported the emergence of some males among the first batch of workers in such colonies. Carbon dioxide-treated bumblebee queens sometimes produced males instead of workers and their nests could be of smaller size than those of overwintered queens (Tasei, 1994; Yoon et al., 2003). Although increased survival rates have been reported in some studies, few studies have attempted to evaluate the effects of different diapause methods, including a combination method of CO2-narcosis and cold treatment, on the survival rates of diapaused queens and their subsequent ability to establish a colony. To evaluate the effects of a combination method of CO2narcosis and cold treatment for diapause break in B. ignitus and B. terrestris queens, we determined whether this method affected their ability to establish a colony after diapause break. This is the first study describing a combination method of CO2-narcosis and cold-treatment application for breaking the diapause of B. ignitus and B. terrestris queens. Materials and Methods Origin of experimental insects The insects used in the experiment were second and sixthgeneration queens acquired from B. ignitus and B. terrestris colonies that were reared year-round in a climate-controlled room (27°C, 65% relative humidity, and continuous darkness) at the Division of Applied Entomology, Department of Agricultural Biology, National Academy of Agricultural Science, Republic of Korea.