All insects, including mosquitoes, are ectothermic, more commonly referred to as “cold-blooded.” Ectotherms rely on external sources of heat, so temperature plays an important role influencing developmental processes, behaviors, and even survival. In general, higher temperatures have been found to shorten development time and decrease adult size of mosquitoes. The phenomenon of having smaller body size in response to increased temperatures is common in ectotherms and tends to be the rule rather than the exception. Although increased temperatures commonly result in smaller size, more rapid growth and development leads to increased probability of survival to adulthood. In the case of nuisance mosquitoes, this may translate into more active adults and more mosquito bites, given there is sufficient precipitation to prevent drying of larval habitats. As we enter the cooler months, we can see some seasonal trends from our mosquito surveillance in Richmond County.
Numbers of nuisance mosquitoes have remained high in some locations through September and arboviral disease (viruses transmitted by arthropods like ticks and mosquitoes) transmission is still a possibility. However, those numbers are beginning to fall due to cooler night temperatures.
Past studies have found that the seasonal emergence of host-seeking females (those seeking a blood meal) is strongly influenced by the minimum temperature, and our results are in agreement with that finding. Furthermore, one study from Italy on the Asian tiger mosquito, a major nuisance species in our area, identified a threshold for activity around 48.2°F – 55.4°F.
A closer examination of our data shows that numbers of mosquitoes vary by one order of magnitude (difference between 10’s and 100’s) when daily low temperatures are around 50°F. These data also show that once daily low temperatures exceed 50°F, the minimum temperature has almost no effect on the number of mosquitoes. As low temperatures in your area begin to drop consistently into the low 50’s, expect a substantial decrease in the number of mosquitoes around your home.