Sefer HaChinuch ספר החינוך

To not eat of swarming creatures that exist from decay: To not eat of swarming creatures that exist from decaying matter — even though they are not from a known species and do not exist from male and female — as it is stated (Leviticus 11:44), “and you shall not defile your souls with any swarming creature that crawls upon the ground.” And the language of Sifra, Shemini, Chapter 12:4 is “‘Swarming creature that crawls upon the ground’ - even though it does not give fruit and multiply.” And Rambam, may his memory be blessed, wrote that “swarming” is stated about a swarming thing that is born from a male and female and “crawling” is stated about one that is made from decay. But Ramban, may his memory be blessed (on Sefer HaMitzvot, Shorashim 9, s.v. vehaperush) challenged him from verses that are written; and he wrote that in all of them, [both] swarming and crawling are stated.

Its root is well-known.

Its laws are short, such that all of its details can be gathered in one general principle: That all swarming creatures of decayed matter in the world that crawl on the earth have been prohibited to us; except for swarming creatures from the decay of fruit that were produced there after they were detached [and] swarming creatures from decaying matter in the waters that are in vessels — it is all like we said above (Sefer HaChinukh 163).

And it is practiced in every place and at all times by males and females. And one who transgresses it and eats a creature from any of the decaying matter in garbage dumps or in any place, even the smallest of the small — once he has eaten it and it was whole — is lashed for it. And if it was not whole, its measure is with a kazayit, as we said.