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Why do Aedes canadensis mosquito eggs need cold exposure before hatching?

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The image shows a group of Virginia big-eared bats sleeping upside down in a dark cavern. — Dormancy Virginia big-eared bats (*Corynorhinus townsendii virginianushibernating*) are true hibernators, entering a state close to death for much of the winter.

The eggs of the Aedes canadensis mosquito enter a state of diapause, a period of suspended development, to survive unfavorable environmental conditions. While some mosquito species only require the presence of water to break this dormancy, Aedes canadensis eggs possess a specific physiological requirement: they must be exposed to cold temperatures before they will hatch.1

This biological mechanism ensures that the eggs remain dormant throughout the summer and autumn, even if they are submerged in water. By requiring cold exposure, the species is synchronized to overwinter and hatch specifically in spring rain pools, rather than hatching prematurely during late summer rains like other species that share the same habitat. This adaptation allows the larvae to emerge at a time when environmental conditions are suitable for their development.1