Mosquitoes are highly sensitive to environmental conditions, particularly temperature. As ectotherms, their internal body temperature directly mirrors their surroundings, making external temperatures a primary factor influencing their survival, activity, and reproduction. Understanding these thermal thresholds helps comprehend mosquito populations and their public health impact.
Mosquitoes and Cold: The Lethal Threshold
Mosquitoes struggle to survive in cold temperatures, with most species becoming inactive when temperatures fall below 50°F (10°C). Below this point, their metabolic processes slow significantly, hindering their ability to fly, feed, and reproduce effectively. Prolonged exposure to temperatures at or below freezing, 32°F (0°C), is lethal for adult mosquitoes.
While adult mosquitoes are vulnerable to freezing, different life stages have varying cold tolerance. Mosquito eggs are often adapted to withstand sub-zero temperatures, remaining dormant until warmer conditions return. Larvae and pupae are also susceptible to cold; their development is interrupted or halted in chilly conditions. For instance, Aedes aegypti larvae die at temperatures around 46°F (7.8°C).
Mosquitoes and Heat: The Lethal Threshold
Extreme heat poses a threat to mosquito survival. Adult mosquitoes cannot survive temperatures exceeding 105°F (41°C); temperatures above this are fatal. High temperatures can lead to rapid desiccation, as mosquitoes cannot regulate their body temperature through sweating.
Larval and pupal stages are sensitive to high temperatures. Larvae can die quickly when water temperatures reach 95°F (35°C) or higher. Extreme heat negatively impacts larval survival and adult production. For Aedes aegypti, the upper temperature limit for development is around 34°C (93.2°F).
Temperature’s Influence on Mosquito Survival and Activity
Temperatures outside of lethal thresholds affect mosquito populations. Mosquitoes are most active in warmer conditions, with peak activity around 80°F (26.7°C). Within this optimal range, their life cycle accelerates significantly. For example, the life cycle can complete in as little as 10 days at 80°F, compared to 14 days at 70°F.
Below optimal temperatures, even if not immediately lethal, mosquito activity decreases, and their development slows. This prolonged development time can expose them to predators or environmental changes, reducing overall survival. Moderately high temperatures can shorten the incubation period for diseases within the mosquito, potentially increasing transmission risk. Many mosquito species employ diapause, a dormant state similar to hibernation, to endure unfavorable cold periods. During diapause, metabolic activity decreases, allowing them to overwinter as adults or resilient eggs until warmer conditions return.