Summary
In homes, flea eggs live for 2 to 3 days before hatching. Most eggs and larvae live in carpeting. The microclimate within the carpet fibers is near ideal for developing fleas. As a result, the incubation period is brief.
Fig 1 Days it takes (y-axis) for 50% of flea eggs to hatch at different ambient temperatures (x-axis) while relative humidity is held constant at 75%.
Details
How Long it Takes Flea Eggs to Hatch
Ambient temperature is the primary factor which governs how quickly flea eggs incubate. However, relative humidity (RH) is important for their survival.
Flea eggs develop in sheltered microhabitats. These areas have their own microclimate, where humidity and temperature are moderated. Thus, conditions in the surrounding environment are of little significance.
Fig 2 Environmental conditions required for flea eggs to survive, and days until they hatch.
In Homes
Most flea eggs get deposited indoors within carpeted rooms. Modern carpeting creates a favorable environment for incubating eggs. In a home setting, flea eggs typically hatch into larvae within two to three days of being laid.
In Ideal Conditions
Flea eggs develop rapidly in warm, humid environments. They’ll hatch within 1.5 days when conditions are optimal Fig 1. Ideal conditions occurs at temperatures near 89.6°F (32°C), and humidity between 75-92%. Nearly all eggs will survive and hatch in these conditions.
In Poor Conditions
As temperature is lowered, the eggs take progressively longer to develop. In poor conditions, it can take 8-12 days for flea eggs to hatch.
Failure to Hatch
Cat flea eggs can’t withstand large fluctuations in temperature or humidity. For example, the eggs will die outdoors during the winter due to the cold, arid air. They don’t go dormant.
Extreme Dryness
In dry conditions, flea eggs will desiccate without hatching. A relative humidity below 50% is often lethal. While 80% of flea eggs survive when RH exceeds 50%. In one study, the eggs survived in as low as 33% RH Fig 3. However, hatching larvae quickly died in these environments, as they’re even more vulnerable to desiccating than eggs.
Fig 3 Percent of flea eggs that survive (y-axis) throughout different increments of relative humidity (x-axis), at three constant ambient temperatures.
Extreme Cold
Cold temperatures are lethal to flea eggs. The lowest temperature they can survive, hatch, and continue developing at is 55.4°F (13°C). Eggs hatch after 12 days at 50.4°F (10°C), but first instar larvae die within 10 days. Flea eggs completely fail to develop below 46.4°F (8°C) Fig 4.
Fig 4 Percent of eggs that survive (y-axis) at three different ambient temperatures across 10 days (x-axis).
Extreme Heat
At the other extreme, flea eggs can’t survive when continuously exposed to any temperature above 100.4°F (38°C). They’ll survive and hatch in 1.5 days at 95°F (35°C). However, this temperature is still too hot for fleas to fully mature into adults.
Higher temperatures require a higher humidity to prevent eggs from desiccating. When exposed to 95°F (35°C), the eggs die at any RH below 75%. Fully saturated air is also lethal at this temperature due to heat accumulating within the eggs. Even at the optimal RH of 75%, only 40% of eggs hatch.
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