Effect of Temperature and Photoperiod on Development, Survival, and Growth Rate of Mealworms, Tenebrio molitor

SIMPLE SUMMARY: The mealworm, i.e., larvae of Tenebrio molitor, has recently been used as a substitute for conventional meat, as it has several advantages, e.g., a lower environmental impact. Knowledge of the effects of temperature and photoperiod on mealworm development is crucial to increase farming efficiency, and to contribute to a sustainable production process. As such data is scarce, we tested the effects of three different temperatures, in combination with three photoperiods, on mealworm survival, development, and growth. We found that temperature strongly affects the survival rate, developmental time, and growth rate of T. molitor larvae. Furthermore, photoperiod influences the developmental time and growth rate. The highest survival rates and growth rates, and shortest developmental times, were observed at 25 and 30 °C at constant darkness. These results are important to improve the mass rearing of mealworms for a sustainable production of food and feed. ABSTRACT: Insects are a potential substitute for conventional meat and can be part of a sustainable human diet due to their valuable nutrients and relatively low environmental production impact. One species that is already produced for human consumption and livestock feed is the mealworm, i.e., larvae of Tenebrio molitor. Knowledge of the effects of temperature, and particularly photoperiod, on mealworm development is scarce, but crucial for the improvement of rearing. Therefore, the effects of three temperatures (20 °C, 25 °C, and 30 °C), in combination with three photoperiods (long-day—16 h:8 h light:dark; short-day—8 h:16 h light:dark, and constant darkness) on mealworm survival, developmental time, and growth rate were tested. We describe a significant effect of temperature on survival rate, developmental time, and growth rate. Furthermore, significant effects of photoperiod on developmental time and growth rate were found. At 25 and 30 °C and constant darkness, the highest survival and growth rate, along with the shortest developmental time, were observed. Our data can be used to improve the mass rearing of mealworms for an efficient production of food and feed.