Female fleas can lay 30 to 50 eggs per day for four to 25 days, depending on the species. Eggs turn into larvae, which develop into pupae, which emerge from cocoons as adults.
Larval fleas go through three stages in which they moult their skin. In all stages, they appear relatively similar--white, light-coloured or nearly transparent.
Worm-Like and Hairy
Larval fleas look much like worms, caterpillars or grubs, with segmented bodies that can curl. Tiny, bristly hairs poke out at intervals along the body.
Larval fleas are approximately .102 inches long, depending on the species. This means most people will not notice them without a microscope. When fleas are seen, they are usually adults.
Apperance with the Naked Eye
The core of a larval flea appears black with the naked eye. This black spot is located toward the head.
Appearance Under a Microscope
Under a microscope, the black core's true nature can be viewed. It is actually bright red, not black, and constitutes the stomach of the creature in the process of digesting blood from faeces produced by adult fleas.
Flea larvae have tiny mouth parts protruding from the bottom of the head. They are difficult to distinguish, even under a microscope, but are used for feeding.