The effect of temperature on the development of the predators Nephus includens (Kirsch) and Nephus bisignatus (Boheman) (Coleoptera: Coccinellidae) was studied. The duration of the development of immature stages and the pre-oviposition period of the two predators, reared on Planococcus citri (Risso) (Homoptera: Pseudococcidae) at eight constant temperatures (10, 15, 20, 25, 30, 32.5, 35, and 37.5 Ϯ 1ЊC), have been recorded. The developmental zero (lower temperature threshold) was estimated to

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... 10.9 and 9.4ЊC, and the thermal constant was 490.5 and 614.3 DD for N. includens and N. bisignatus, respectively, using the linear model. Data were Þtted to various nonlinear temperature-dependent models, and the thermal developmental thresholds (lower and upper), as well as the optimum temperature for development, have been estimated. Evaluation of the models took place, based on the following criteria: Þt to data (residual sum of squares and coefÞcient of determination or coefÞcient of nonlinear regression), number and biological value of the Þtted coefÞcients, number of measurable parameters, and accuracy on the estimation of the thresholds. Conclusively, linear and Lactin models are highly recommended for the description of temperaturedependent development of these two predators and possibly of other coccinellids.