Effects of temperature on the development and survival of an endangered butterfly, Lycaeides argyrognomon (Lepidoptera: Lycaenidae) with estimation of optimal and threshold temperatures using linear and nonlinear models

The effects of temperature on the development and survival of Lycaeides argyrognomon were examined in the laboratory. The eggs, larvae and pupae were reared at temperatures of 15, 17.5, 20, 25, 30 and 33°C under a long-day photoperiod of 16-h light and 8-h darkness. The survival rates of the first–third instars ranged from 40.0 to 82.4%. The mortalities of the fourth instar were lower than those of the first–third instars. The development time of the overall immature stage decreased from 78.33 days at 15°C to 21.07 days at 30°C, and then increased to 24.33 days at 33°C. The common linear model and the Ikemoto–Takai model were used to estimate the thermal constant (K) and the developmental zero (T0). The values of T0 and K for the overall immature stages were 10.50°C and 418.83 degree-days, and 9.71°C and 451.68 degree-days by the common model and the Ikemoto–Takai model, respectively. The upper temperature thresholds (Tmax) and the optimal temperatures (Topt) of the egg, the first–third instars and the overall immature stages were estimated by the three nonlinear models. The ranges of Topt estimated were from 30.33°C to 32.46°C in the overall immature stages and the estimates of Tmax of the overall immature stages by the Briere-1 and the Briere-2 models were 37.18°C and 33.00°C, respectively. The method to predict the developmental period of L. argyrognomon using the nonlinear models was discussed based on the data of the average temperature per hour.