Temperature is a key environmental factor affecting the growth, development, survival and reproduction of insects. Although it is widely known that the relationship between temperature and insect development rate is nonlinear, model‐based studies have been conducted to investigate the global warming impacts on insect voltinism using the degree‐day approach based on a linear model. In the present study, the wheat armyworm Mythimna sequax (Franclemont) was used as a model organism to test whether voltinism estimated under current and future climate conditions varied among phenological models, locations and climate change scenarios. In general, voltinism increased in different years and climate change scenarios compared with current climatic conditions. The degree‐day overestimated the number of generations compared with the nonlinear models and also predicted an increase in voltinism in the entire study area as a result of global warming. Location, phenological model and the interaction between these factors explained 94% of the variance in the estimated voltinism. The results obtained in the present study reveal that the choice of phenological models affects voltinism predictions and that a nonlinear model can be used to understand the effects of climate change on insect voltinism, especially in regions where temperature will reach the upper threshold of a species more often.

The small tomato borer, Neoleucinodes elegantalis (Guenée, 1854) is a multivoltine pest of tomato and other cultivated solanaceous plants. The knowledge on how N. elegantalis respond to temperature may help in the development of pest management strategies, and in the understanding of the effects of climate change on its voltinism. In this context, this study aimed to select models to describe the temperature-dependent development rate of N. elegantalis and apply the best models to evaluate the impacts of climate change on pest voltinism. Voltinism was estimated with the best fit non-linear model and the degree-day approach using future climate change scenarios representing intermediary and high greenhouse gas emission rates. Two out of the six models assessed showed a good fit to the observed data and accurately estimated the thermal thresholds of N. elegantalis. The degree-day and the non-linear model estimated more generations in the warmer regions and fewer generations in the colder areas, but differences of up to 41% between models were recorded mainly in the warmer regions. In general, both models predicted an increase in the voltinism of N. elegantalis in most of the study area, and this increase was more pronounced in the scenarios with high emission of greenhouse gases. The mathematical model (74.8%) and the location (9.8%) were the factors that mostly contributed to the observed variation in pest voltinism. Our findings highlight the impact of climate change on the voltinism of N. elegantalis and indicate that an increase in its population growth is expected in most regions of the study area.

Insect development is affected by temperature which in turn influences population growth. The thermal limits tolerated by insects vary depending on the species which can have important consequences for their voltinism in a climate‐changing world. This study used a multicriteria approach to select the best among six nonlinear models to describe the temperature‐dependent development rate of Anticarsia gemmatalis and Spodoptera cosmioides, two important soybean pests. The best models for each species were employed to estimate their voltinism under current and future climate conditions predicted for southern Brazil. According to the selected models, A. gemmatalis showed high upper lethal threshold (42.4°C) than S. cosmioides (32.3°C). Such disparity in the tolerance to high temperatures resulted in pronounced differences in the species' voltinism in southern Brazil, especially under future climate conditions. While an increase in the voltinism of A. gemmatalis of up to 32.3% was predicted in the entire study area, a decrease in the voltinism of S. cosmioides of up to 33.1% was predicted in warmer regions where temperatures more often exceeded the species' optimum. The species, location, and interaction between these two factors explained 96.0% of the total variation observed in the voltinism. Our findings suggest that disparity among species in their tolerance to high temperatures may differently influence their voltinism and population growth, leading to potential changes in their status as a pest in some regions due to climate change.