I have had gnats/fruit flies in my litter boxes before. Usually during warm weather when I got lazy about cleaning them, but a good scooping is usually all it takes to get rid of them. I used to have far more cats than I really could take proper care of The two boys I have now are a far more manageable number.
Fleas do not fly and really don't crawl, they jump. And they have a distinctive shape, once you see one, or even a picture of one, you know exactly what they are. But as others have said, fleas don't go in the litter box. I've never seen fleas in a litter box. They are in carpet, bedding, and on the animals themselves. Not to mention they bite, and you will know if you're being bitten. I'd rather deal with gnats or fruit flies than fleas, that's for sure! The gnats are much easier to get rid of.
Fleas do not fly and really don't crawl, they jump. And they have a distinctive shape, once you see one, or even a picture of one, you know exactly what they are. But as others have said, fleas don't go in the litter box. I've never seen fleas in a litter box. They are in carpet, bedding, and on the animals themselves. Not to mention they bite, and you will know if you're being bitten. I'd rather deal with gnats or fruit flies than fleas, that's for sure! The gnats are much easier to get rid of.