Geographical Variation in Diapause Intensity and Threshold Temperature in the Eggs of a Cricket,Teleogryllus emma(Orthoptera: Gryllidae)

Diapause intensity, threshold temperature and effective temperature of three populations of Teleogryllus emma (Orthoptera: Gryllidae) collected from Jining (35°10′), Sihong (33°46′) and Changsha (27°02′), China, were investigated. The results showed that the diapause intensity for eggs of T. emma was stronger for the Changsha population at lower latitude than for the Sihong and Jining populations at higher latitudes, whereas no significant difference in the egg diapause intensity was found between the Sihong and Jining populations. A latitudinal increase in egg threshold temperature was observed for the Changsha, Sihong, and Jining populations at 12.2°C, 14.0°C, and 14.7°C, respectively, while an inverse trend in egg effective temperatures was observed in the three populations at 240.1, 215.6, and 196.1 day-degrees, respectively. The results revealed distinct geographical clines among local populations of T. emma in several key life history characteristics for the egg stage, including diapause intensity, threshold temperature and effective temperature, suggesting that the species has evolved different life history strategies in accordance with local climate conditions.