A single cat flea weighs 0.45 to 1.08 mg, depending on whether it has fed or not. Male fleas weigh less than females.
Fig 1 Cat flea weight in mg (y-axis) during the first 72 hours of feeding on a cat (x-axis).
After emerging from her cocoon, a female cat flea weighs around 0.45 mg. Her weight dramatically increases once a host is acquired and feeding begins. Her weight increases by 40% within an hour of feeding. In 12 hours, she’ll have increased in weight by 75%. She’ll be fully engorged within 48 hours of feeding, weighing roughly 1.08 mg, which is an increase of 140%. While actively reproducing, females weigh an average of 0.947 mg.
Male cat fleas are smaller than females and have smaller abdomens. As a result, the males weigh less and don’t get much heavier after feeding. Unfed males weigh 0.36 mg. In an hour of feeding, they’ll increases in weight by 3%. They achieve their maximum weight of 0.43 mg after 36 hours of feeding, a 19% increase.
In a mixed sex study, unfed cat fleas weighed an average of 0.192 mg. They nearly doubled their weight to 0.343 mg after 24 hours of feeding.