Img 1 An adult cat flea parasitically feeding off a host and defecating.
Fleas do poop. Their excreta is commonly called flea dirt. On average, cat fleas produce 0.645 to 0.770 mg of feces a day. It consists of dry host blood, and appears as tiny black specks. Fleas poop directly on dogs or cats. When the animal grooms itself, the feces falls into the environment.
How Much Fleas Poop
Consuming Extra Blood
Fleas imbibe much more blood than they can use. Their guts hold around 5 µl of blood, but they ingest an average 6.97 µl of blood per day. An egg-laying female can imbibe 13.6 µl of blood each day, equivalent to 15 times her body weight. As a result, fleas produce large amounts of feces while feeding.
Amount of Feces Produced
Fleas feed randomly for 2-3 minutes at a time. During each feeding, they produce 8-10 droplets of feces. The average flea expels 0.645 to 0.770 mg of poop per day. Females produce a much greater volume of feces than males, often around 17 times as much (0.85 vs 0.05 mg daily).
Flea Poop is Undigested Host Blood
Flea guts contain specialized enzymes to digest host blood. However, only the blood nearest to midcut cells gets processed. Most doesn’t get utilized. The blood rapidly passes through the midgut, to the hind-gut, and is expelled out the anus. Thus, flea dirt consists primarily of undigested host blood.
What Flea Poop Looks Like
As the fecal blood dries, it breaks apart into irregular shapes. The dry blood appears as dark red or black specks Img 2. It’s often said to resemble ground pepper or black dandruff. There are two types of feces: round spherules (0.07-0.25 mm), and long coils (0.84 mm).
Where to Find Flea Poop
The most common place to find flea poop is on pets. Adult fleas live on their hosts and rarely leave. Thus, all biological functions, including defecation, occur on the animal Img 1. The feces initially gets lodged in pet fur, but it eventually drops out when the animal grooms itself.
Img 2 Dry flea poop appearing as black specks in a cat’s fur.
Diagnosing an Infestation with Flea Dirt
A good way to diagnose a flea infestation is to find flea dirt on pets. Since the feces consists of blood, using water is a good way to identify it. The dry poop will smear into a red stain when rubbed onto a wet paper towel Img 3. Similarly, the blood will reconstitute inside a droplet of water, turning it red.
Img 3 Rubbing dry blood feces on a wet paper towel causes it to reconstitute and smear red.