A SAS procedure for estimating parameters of the SSI model describing temperature-dependent developmental rates in insects
Author of the article:SHI Pei-Jian1, 2** GE Feng1***
Author's Workplace：1. State Key Laboratory of Integrated Management of Insect Pests and Rodents in Agriculture, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; 2. Bamboo Research Institute, Nanjing Forestry University, Nanjing 210037, China
Key Words： cotton bollworm, developmental time, parametric fitting, thermal environment, intrinsic optimum temperature for development
Abstract： The Sharpe-Schoolfield-Ikemoto (SSI) model is a very important mathematical equation that is widely used to describe the effect of temperature on the developmental rates of insects. This model is not only a good fit to data on temperature-dependent developmental rates, but also provides estimates of several valuable thermal parameters, especially the intrinsic optimum temperature for development (TΦ) that indicates the optimal thermal environment for a specific insect species. However, the SSI model has considerable difficulty in estimating parameters then making it rather complex to use. A package for estimating these parameters has been developed based on the statistical software R. Because some domestic resea-rchers might prefer to use the statistical software SAS, we here present a practical SAS procedure for quickly estimating SSI model parameters. This procedure exhibited satisfactory goodness of fit to the temperature-dependent developmental rates of male pupae of cotton bollworms. These results further demonstrate the validity of the SSI model for describing the effect of temperature on insect developmental rates.