The Canadian Entomologist



R. E. Stinnera1, A. P. Gutierreza2 and G. D. Butler Jr.a3

a1 Department of Entomology, North Carolina State University, Raleigh

a2 Division of Biological Control, University of California, Berkeley

a3 Western Cotton Research Laboratory, U.S. Department of Agriculture, Phoenix, Arizona


With the current advances in insect population modelling, the need for more accurate simulation of temperature-dependent growth rates has become vital. The day-degree concept, with its linear temperature–rate relationship, has not been adequate for simulation of field populations under highly variable temperature conditions. Similarly, several of the non-linear relationships proposed in the past (Janisch’s catenary, parabola) have also been inadequate. All of these relationships produce large errors at temperature extremes.

This paper presents a comparison of various functions which have been used for developmental time estimation and an algorithm for a sigmoid function which can be used in simulations having either a calendar or a physiological time base. Validation of the algorithm is presented for three insect species.

(Received October 29 1973)


1 This research was supported in part by NSF Grant GB28855.

2 Paper No. 4197 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh.