When do fleas lay eggs?


Female fleas begin laying eggs 1-2 days after consuming their first blood meal. Unfed females can’t produce eggs, and unfed males can’t inseminate females. Egg production peaks 4-9 days after feeding is initiated. Females continue laying eggs throughout their lives, at a slowly declining rate.


When Oviposition Begins


Cat fleas are anautogenous, which means a blood meal is required before they can successfully mate and reproduce.


Unfed female fleas can’t produce eggs. They have underdeveloped ovaries which are blocked by a follicular plug. The first blood meal triggers the ovaries to develop and leads to sexual maturation. Female fleas must continually feed to keep their metabolism in balance for egg production.


Blood feeding is also required by male fleas before they can inseminate a female. Unfed males won’t even attempt to mate. In unfed males, a testicular plug prevents the passage of sperm from the testes. The plug dissolves within 24 hours of consuming their first blood meal.


Cat fleas aren’t parthenogenetic (asexual). Eggs must be fertilized through successful mating in order to produce offspring. Virgin females can lay eggs, but none will be viable. Upon mating with males, they’re able to oviposit viable eggs and output quadruples. Maximum fertility occurs when a female successively mates with multiple male partners. Multiple-mated females lay 9 times as many viable eggs as single-mated females.

Course of Events

Upon emerging from cocoons, adult fleas quickly seek a host for a blood meal. In fact, they may not even emerge until a suitable host is nearby. Once a host is acquired, fleas begin feeding within minutes. They then mate within 8-24 hours. Egg production begins in 24-48 hours after the first blood meal.

When placed on a host, day-old females take 3-4 days to begin producing eggs, while 4-day old females lay eggs within 48 hours. In natural settings, young females delay their host-seeking behavior. This gives their reproductive systems time to mature off the host, thus increasing the chance of producing eggs before they’re killed from host grooming.

Peak Egg Production

Egg production rates begin low but rise quickly. Peak production occurs 4-9 days after the first blood meal (5-10 days after cocoon emergence). A high level of production is maintained for 2-4 weeks before tapering off. Females can continue laying eggs for over 100 days at a slowly declining rate. Though, in most cases, fleas only survive for around a week.

Egg Production throughout a Day

Fleas continually lay eggs throughout the day. However, oviposition rates peak in the middle-to-end of the scotophase (dark cycle) Fig 1. There’s also a minor peak in middle of the photophase (light cycle).

There’s no correlation between the rate of egg laying and the host’s sleeping patterns. And different lengths of daylight, simulating different seasons, have no effect on egg production.

Fig 1 Number of eggs produced per cat flea (y-axis) at every hour across a day (x-axis). The scotophase (dark cycle) occurred from 1800 to 0600 hours.


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