How long do flea larvae live for?

Summary

In homes, flea larvae live for 7-11 days before pupating. In ideal environments, they can fully develop in 4-7 days. In poor conditions, it may take 28-45 days for flea larvae to mature. How quickly they develop depends upon ambient temperature, relative humidity, and food availability.

Details

Larval Growth Rates

In Homes

In the average home environment, the larval stage of cat fleas typically lasts for 7 to 11 days. Modern carpeting provides a favorable habit for developing flea eggs and larvae (baby fleas).

In Ideal Conditions

Ideal flea larvae environments are warm, humid, and contains plenty of food. Under these conditions, the larvae can fully mature in as little as five days Fig 1.

Fig 1 Days it takes (y-axis) for 50% of flea larvae to form cocoons at different ambient temperatures (x-axis) while relative humidity is held constant at 75%.

In Poor Conditions

In unfavorable conditions, flea larvae may live for 28 to 45 days before pupating. Prolonged development occurs due to low humidity, cool temperatures, oxygen tension, and food shortages.

Temperature, Humidity & Food

The two primary factors governing how quickly larvae develop are relative humidity (RH) and ambient temperature. However, surrounding conditions are somewhat irrelevant, because flea larvae live in protected microhabitats. These areas have their own sheltered microclimates, where humidity is maintained and temperature is moderated.

flea larvae conditions

Fig 2 Environmental conditions required for flea larvae to survive, and days it takes the larvae to fully develop from egg to cocoon.

Relative Humidity

A relative humidity of 75-92% is optimal for immature fleas. Larvae begin forming cocoons in 5 days at 90% RH, while taking twice as long at 50% RH. In a similar study, larvae raised at 65-85% RH took 4-5 days to develop, while taking 12 days at 50% RH.

The ideal RH occurs above 80%. Only 30% of larvae survive at 70% RH, while over 60% reach adulthood at 80-90% RH. Additionally, larvae are able to actively uptake water from the air when RH exceeds 75%. The larvae exposed to a higher RH develop into larger, healthier adults.

Ambient Temperature

The optimal temperature for flea larvae occurs between 80.6°F and 89.6°F (27°C and 32°C). 88% of larvae survive at these temperatures and 75% RH. Many complete development within five days. Other studies corroborate this data. In one, the ideal temperature occurred between 77°F and 86°F (25°C and 30°C). In another, 99% of larvae survived at 90°F (32.2°C) and 80% RH. Some reached maturity in as little as four days.

Time to maturity progressively increases as temperature is lowered. At 69.8°F (21°C), 50% of larvae mature within 12 days. At 55.4°F (13°C), larvae don’t form cocoons until day 28. A different study found complete development took 45 days at 59°F (15°C).

Food Shortages

Food shortages can result in insufficient nutrition and nearly double the time it takes larvae to develop. Additionally, malnourished larvae become slightly smaller adults.

Desiccation & Death

Humidity Extremes

Of all life stages, larvae are most susceptible to death from desiccation. This makes them very sensitive to humidity. Extremes occur at 50% and 95% RH.

Low-End

All flea larvae will desiccate when exposed to a RH below 50%, regardless of temperature. One experiment saw a slightly higher low-end extreme, with a RH of 60% being lethal. However, a different study showed that at 50%, 55%, and 65% RH, larval survival was 24%, 77% and 91%, respectively Fig 3.

Fig 3 Percent of flea larvae that survive (y-axis) at different increments of relative humidity (x-axis) while ambient temperature is held constant at 90°F.

High-End

At the other extreme, no larvae can survive at 95-100% RH, because of fungal growth on their substrate and food.

Temperature Extremes

Flea larvae can only survive at temperatures between 55.4°F and 95°F (13°C and 35°C).

Low-End

Larvae die at any temperature below 55.4°F (13°C). Similarly, one study found the low-end temperature occurred at 59°F (15°C). At 50°F (10°C), flea larvae die within 10 days of hatching from eggs. At 46.4°F (8°C) and 75% RH, 65% of larvae die within 10 days, and all perish by day 20. At 37.4°F (3°C), 37% die within a day, and 100% die within five days.

High-End

Temperatures above 95°F (35°C) are lethal to flea larvae. Only 30% live long enough to form cocoons, and they’ll never emerge to complete their development into adults. Outdoors, when temperatures exceed 95°F (35°C) for more than 40 hours a month, there’s complete mortality in flea larvae.

60°F
80°F
95°F

Fig 4 Percent of flea larvae that survive (y-axis) throughout different increments of relative humidity (x-axis), at three constant ambient temperatures.

Starvation

Unfed cat flea larvae will die from starvation within three days if they’re unable to find food.

References

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Discussion

  • Sherry November 25, 2016, 2:58 pm

    I have a slight flea problem with my dog. I put all his toys and clothes in a garbage bag in the freezer to kill the fleas. My question is how long should I keep these items in the freezer so the eggs and larvae die. I bought precor and have not received it yet and that is to spray the house. I also got pills from the vet that will start killing the fleas on my dog withing 30 minutes. I am washing all bedding, vacuum everything.

    • Adam Retzer November 26, 2016, 1:59 pm

      Hello Sherry, it sounds like you should have the fleas under control soon. To answer your question: No fleas, regardless of life stage, should be able to survive long in a freezer. Eggs are larvae are the most vulnerable stages. Nearly all should be dead within a day. However, you may want to leave the items in the freezer for up to 5 days, just for the extra degree of certainty.

  • Christine Watson February 5, 2017, 8:33 pm

    My home has been cat free for nearly 7 months. I had a heavy infestation of fleas while my cat was alive and I treated all rooms with fumigators and sprays. I have not seen any fleas or flea dirt for approx 5 months. I am due to have a kitten in a few weeks time and I want to know if any fleas, flea eggs or pupa will still be surviving in my home after this length of time without a host. Thanks.

    • Adam Retzer February 6, 2017, 6:44 pm

      You should be in the clear. The longest a flea could survive for is around 6 months. In homes, the life cycle from egg to adult completes in 17-26 days. Mature adults can stay inside their cocoons in a quiescent state for up to 5 months (most don’t). The pre-emerged adult is the only stage that can enter into a dormant-like state with extended longevity.

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