Alterations in pest ecology due to climate change can affect crop production. Understanding the rate and period of pest development is essential for predicting population dynamics and determining the optimal timing for pesticide application to ensure stable crop production. In this study, we aimed to develop a mechanical method for determining the developmental periods of rice planthoppers and evaluate the impact of climate change on these periods over a 42-year period. We evaluated interannual variations in the developmental periods of two rice pests, Nilaparvata lugens (Stål) and Sogatella furcifera (Horváth), using light traps to capture data between 1980 and 2022 from 20 areas in Kyushu, Japan, a region of East Asia severely affected by rice planthopper outbreaks. Meteorological data revealed a trend of increasing daily mean temperature (2.2-4.5 × 10 °C year). A significant correlation was also detected between the length of developmental period and temperature (P < 0.001). For both N. lugens and S. furcifera, a significant trend toward progressively shorter developmental periods was observed over time, even after accounting for differences in the starting dates of development (P < 0.01). These results indicate that for pests, developmental periods have been progressively shortening in response to warming associated with climate change. This study provides important insights for predicting future pest ecology under climate change conditions based on results obtained from rearing experiments conducted in laboratory. © 2026 Society of Chemical Industry.