Flies prefer heat, but only within a specific range. Warmth stimulates their activity and reproduction, with an optimal temperature zone where they thrive. Temperatures outside this favorable range, whether excessively hot or significantly cold, can be detrimental to their survival and development. This relationship provides insight into their behavior and population dynamics.
Flies’ Preferred Temperatures
Flies, being cold-blooded, depend on external heat to regulate their body temperature, which directly influences their activity levels. Most common species, like house flies, are active and abundant between 27°C and 32°C (80°F to 90°F). Fruit flies prefer 23°C to 28°C (73°F and 82°F). Within these ranges, warmth significantly increases their metabolic rate.
An elevated metabolic rate leads to more frequent feeding, increased flying activity, and higher rates of reproduction. This explains why fly populations become more prevalent during warmer months, particularly in summer. As temperatures rise towards their optimal zone, increased heat allows flies to move, find food, and mate more efficiently, contributing to their abundance.
Temperature’s Influence on Fly Life Cycles
Temperature profoundly impacts a fly’s entire life cycle, from egg to adult, dictating development speed. Warmer temperatures significantly accelerate progression through each stage: egg laying, larval development, and pupation. For instance, house fly eggs, which typically take 20 hours to hatch, can hatch in less than 8 hours at approximately 37°C (99°F).
In very warm environments, the entire life cycle of a house fly can be completed in as little as four days. Conversely, cooler temperatures slow these developmental processes, extending the duration of each life stage. This allows flies to complete multiple generations quickly, leading to rapid population expansion during warm seasons.
How Flies Cope with Extreme Temperatures
When temperatures move beyond their optimal range, flies face severe consequences or employ various strategies. Above approximately 35°C (95°F), their activity decreases as they conserve energy and avoid desiccation. Extreme heat is lethal, with temperatures above 40°C to 49°C (104°F to 120°F) proving fatal for many species. To mitigate heat stress, flies may seek cooler, shaded areas or move indoors.
In contrast, extreme cold poses different challenges. As temperatures drop, cold-blooded flies become less active and seek sheltered locations. Many species enter a state of dormancy known as diapause, characterized by reduced metabolic activity and suspended development. This allows them to conserve energy and withstand harsh winter conditions. While adult flies often perish in freezing temperatures, some species survive by overwintering as larvae or pupae, or by producing natural “antifreeze” compounds like glycol.