Mosquitoes are cold-blooded insects highly sensitive to surrounding temperatures. These thermal conditions directly influence their survival, development, and activity.
Mosquitoes and Cold Temperatures
Adult mosquitoes become inactive when temperatures consistently drop below 10°C (50°F). Their metabolic processes slow down, affecting their ability to fly, feed, and reproduce. Freezing temperatures, typically below 0°C (32°F), are lethal for most adult mosquitoes not in a dormant state.
Many mosquito species employ diapause, a suspended development similar to hibernation. During diapause, some adult female mosquitoes seek sheltered locations like basements or hollow logs to overwinter, reducing their metabolic activity. While many adults die off, the species can persist through these overwintering stages.
Mosquitoes and Hot Temperatures
Extremely high temperatures pose a significant threat to adult mosquito survival. Temperatures exceeding 35-38°C (95-100°F) can be lethal due to dehydration and metabolic stress. Mosquitoes are ectothermic, meaning their body temperature mirrors their environment, and prolonged heat exposure can be fatal.
While warmth generally accelerates their life cycle, excessive heat can impair reproduction and reduce activity. Adult Anopheles mosquitoes, for instance, find temperatures above 36°C near their upper thermal limit for development. Mosquitoes often seek cooler, shaded areas during the hottest parts of the day to avoid direct sunlight and mitigate heat stress.
Survival Stages: Eggs and Larvae
Mosquito populations persist through adverse conditions thanks to the resilience of their eggs and larvae. Mosquito eggs, especially from floodwater species like Aedes, can diapause, surviving freezing, desiccation, and extreme heat for extended periods. These cold-hardy eggs are insulated and remain dormant in soil or dried containers, hatching when favorable conditions return.
Larval and pupal stages, which develop in water, also have specific temperature tolerances. While higher water temperatures generally accelerate larval development, extreme water temperatures can be lethal. For instance, Anopheles gambiae eggs show optimal hatching between 24-30°C, with significantly reduced viability at 12°C or 42°C.
Temperature’s Impact on Mosquito Populations
Temperature fluctuations throughout the year directly influence mosquito population dynamics. Warm seasons, typically between 25-28°C (77-82°F), lead to accelerated breeding cycles, increased metabolism, and higher activity levels, often resulting in rapid population growth. Conversely, cold seasons or extended periods of extreme heat cause populations to decline or enter dormancy.
Temperature affects various life history traits, including development rates, adult mortality, and biting rates, which in turn impact the potential for disease transmission. For instance, the extrinsic incubation period (EIP), the time it takes for a pathogen to develop within a mosquito before it can be transmitted, is highly temperature-dependent, shortening at warmer temperatures. Understanding these thermal sensitivities is important for predicting mosquito-borne disease risk and developing effective control strategies.