Bioclimatic Thresholds, Thermal Constants and Survival of Mealybug, <i>Phenacoccus </i><i>solenopsis</i> (Hemiptera: Pseudococcidae) in Response to Constant Temperatures on Hibiscus

<div><p>Temperature-driven development and survival rates of the mealybug, <i>Phenacoccussolenopsis</i> Tinsley (Hemiptera: Pseudococcidae) were examined at nine constant temperatures (15, 20, 25, 27, 30, 32, 35 and 40°C) on hibiscus (<i>Hibiscus</i><i>rosa</i><i>-sinensis</i> L.). Crawlers successfully completed development to adult stage between 15 and 35°C, although their survival was affected at low temperatures. Two linear and four nonlinear models were fitted to describe developmental rates of <i>P</i><i>. solenopsis</i> as a function of temperature, and for estimating thermal constants and bioclimatic thresholds (lower, optimum and upper temperature thresholds for development: T_min, T_opt and T_max, respectively). Estimated thresholds between the two linear models were statistically similar. Ikemoto and Takai’s linear model permitted testing the equivalence of lower developmental thresholds for life stages of <i>P</i><i>. solenopsis</i> reared on two hosts, hibiscus and cotton. Thermal constants required for completion of cumulative development of female and male nymphs and for the whole generation were significantly lower on hibiscus (222.2, 237.0, 308.6 degree-days, respectively) compared to cotton. Three nonlinear models performed better in describing the developmental rate for immature instars and cumulative life stages of female and male and for generation based on goodness-of-fit criteria. The simplified β type distribution function estimated T_opt values closer to the observed maximum rates. Thermodynamic SSI model indicated no significant differences in the intrinsic optimum temperature estimates for different geographical populations of <i>P</i><i>. solenopsis</i>. The estimated bioclimatic thresholds and the observed survival rates of <i>P</i><i>. solenopsis</i> indicate the species to be high-temperature adaptive, and explained the field abundance of <i>P</i><i>. solenopsis</i> on its host plants. </p>