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Tenebrio adaptability to temperature changes
Tenebrio molitor, commonly known as mealworms, exhibits a broad range of temperature adaptability, allowing them to survive in various environments. In northern regions, under natural conditions, both larvae and adult mealworms can endure winter by entering a dormant state. They can withstand temperatures below 10°C in storage facilities, although their survival rate is very low in such conditions. Mealworms begin to die when exposed to temperatures above 35°C. As the temperature drops below 15°C in the fall, they start hibernating. During this period, they continue to feed but do not grow or undergo any developmental changes. Once winter ends and temperatures rise artificially, mealworms can resume feeding, growing, and eventually pupating.
If the temperature in the rearing room is increased to 20°C during winter, larvae can return to normal feeding and progress through the pupal stage. However, for mating and egg-laying, the temperature must be raised to at least 25°C. Therefore, the ideal growth temperature for Tenebrio molitor is between 20°C and 32°C, with the optimal range for growth and reproduction being 25°C to 30°C. The lethal high temperature is around 35°C, beyond which the insects begin to die. However, in some cases, even at 32°C, mealworms may start dying in large numbers. This is often due to high population density, where the continuous movement and friction between individuals generate additional heat, raising local temperatures by 2–5°C. To prevent this, it's crucial to reduce population density and improve ventilation to enhance heat dissipation.
Mealworms are also vulnerable to extreme cold, with death occurring at temperatures below 4°C. In the Guanzhong region of Shaanxi Province, where winter temperatures can remain around 10°C for over 20 days, most mealworms do not freeze to death, indicating their strong cold resistance. Natural temperature changes tend to be gradual, allowing insects to adapt more easily. However, sudden and extreme temperature fluctuations caused by human intervention—such as daily temperature swings exceeding 20°C—can disrupt the mealworms' metabolism, leading to increased disease and mortality.
We have learned from past experiences that inconsistent heating, such as turning on heaters during the day and off at night, creates significant temperature variations. In one case, the indoor temperature in the insect-rearing room fluctuated between 28°C during the day and 8°C at night. These drastic changes weakened the mealworms' immunity, and within a month, all of them died. Like other animals, mealworms are sensitive to rapid temperature shifts, making them prone to illness and death when exposed to unstable environmental conditions.