Regulation of larval diapause by colony-founding queens of Crematogaster teranishii (Hymenoptera: Formicidae)
Keiji NAKAMURA
Department of Biosphere-Geosphere Science, Faculty of Biosphere-Geosphere Science, Okayama University of Science, Ridai-cho 1-1, Okayama 700-0005, Japan; e-mail: nakamura@big.ous.ac.jp
Nuptial flights of Crematogaster teranishii Santschi occur in autumn. Queens and possibly larvae pass the first winter without workers in Okayama, Japan. This study examines and tests the hypothesis that C. teranishii queens regulate not only their own diapause, but also that of their larvae. Some queens collected immediately after their nuptial flight in early October were exposed to a low temperature of 10°C for 3 months before transfer to 25°C; these queens started oviposition approximately 8 days after the transfer. Larvae reared by these previously chilled queens pupated synchronously until day 50. Other field-collected queens reared at 25°C without prior chilling reproduced soon after collection. They started oviposition, but the development of their larvae was arrested and pupation occurred late or not at all within the120 day experimental period. The delay in pupation in colonies in which the queens were not previously exposed to low temperature strongly indicates that many larvae are in diapause. Because eggs and larvae were not exposed to low temperatures, they were unable to determine the developmental pathway providing the best response to environmental factors. Results indicate that queens regulate whether their larvae undergo diapause.
Keywords: Hymenoptera, Formicidae, colony development, ant, larval diapause, reproductive diapause of queens, low temperature, social effect
