Why are there no fleas in winter? - briefly
Fleas cannot survive low temperatures because their eggs, larvae, and adults require warmth and humidity to develop; winter conditions cause mortality and halt reproduction. Consequently, populations disappear until favorable climate returns.
Why are there no fleas in winter? - in detail
Fleas disappear during the cold season because their development is temperature‑dependent. Eggs, larvae and pupae require ambient warmth, typically above 10 °C, to progress. When outdoor temperatures drop below this threshold, the life cycle stalls; larvae cease feeding, and pupae enter a dormant state called diapause until conditions improve.
Host availability also declines. Many animals that serve as blood meals—dogs, cats, rodents—spend more time indoors where heating raises ambient temperature but reduces the flea’s preferred microhabitat. Indoor environments are often cleaned more frequently in winter, removing organic debris that larvae need for nourishment.
Physiological limits of the adult insect contribute as well. Adult fleas cannot survive prolonged exposure to sub‑freezing temperatures; their exoskeleton loses fluid balance and metabolic processes shut down. Consequently, adult populations die off before the onset of sustained cold.
The combined effect of thermal inhibition, host behavior, and adult mortality explains the seasonal absence of these ectoparasites. When spring returns and temperatures rise, dormant pupae complete development, and the cycle resumes.