Relationship between temperature and developmental rate of Stethorus punctillum (Coleoptera: Coccinellidae) and its prey Tetranychus mcdanieli (Acarina: Tetranychidae)

Temperature affects insect and mite development, allowing species-specific traits including optimal temperature and low and high temperature thresholds to be observed. Development rate models and biological parameters estimated from them can help determining if synchrony exists between pests and natural enemies. We studied development of the coccinellid Stethorus punctillum Weise and the spider mite Tetranychus mcdanieli McGregor at 12 constant temperatures ranging 10-38degreesC (+/-0.5degreesC), and modeled their development rates as a function of temperature. This predator-prey complex is typical of red raspberry, Rubus idaeus L., in Quebec, which is characterized by a short season. Eleven published models were compared for accuracy in predicting development rate of all stages of both species, and estimating their temperature thresholds and optima. The spider mite developed to the adult stage in the 14-36degreesC range, compared with 14-34degreesC for the coccinellid. Males and females did not differ, and the development rates steadily increased from 14 to 30degreesC, leveling off in the range 34-36degreesC for the spider mite, or 30-32degreesC for its predator. Most models were rejected for failure to satisfy criteria of goodness-of-fit and estimable temperature threshold parameters. The Lactin-2 model for T mcdanieli and the Briere-1 model for S. punctillum, were superior at estimating low temperature threshold, which is critical where temperatures are frequently low in the spring, and were separately fitted to all development stages of both organisms. Based on the predictable early spring development of S. punctillum and T mcdanieli, the results indicate potential synchrony between them.