TEMPERATURE-DEPENDENT DEVELOPMENT OF MEXICAN BEAN BEETLE (COLEOPTERA, COCCINELLIDAE) UNDER CONSTANT AND VARIABLE TEMPERATURES

Development of immature stages of the Mexican bean beetle, Epilachna varivestis Mulsant, on dry beans, Phaseolus vulgaris L. (cv. 'Maine Yellow eye'), was assessed at six constant temperatures from 15 to 30-degrees-C. Relationships between temperature and developmental rate were described by linear degree-day and nonlinear biophysical models. Minimum threshold values in the degree-day model for the egg, larval, and pupal stages were 8.6, 7.6, and 9.3-degrees-C, respectively. Development of the egg, first, second, third, and fourth instars, and pupae required 98.2, 61.7, 50.5, 60.6, 105.9, and 90.3 degree-days, respectively. First-instar developmental data were fit to a two-parameter biophysical model; egg, second-, third-, and fourth-instar and pupal developmental data were fit to a four-parameter biophysical model with high temperature inhibition. Two laboratory experiments with thermoperiodic regimes and observations from field cage studies showed that the degree-day model resulted in more accurate predictions than the biophysical model.