Why do both the mango and the bee have "Indica" in their binomial name? In my textbook, it is written that the binomial name of mango is _Mangifera indica_ and the binomial name of a bee is _Apis indica_. Now in the name the second part is the name of species. But mango and bee are not the same species. One is a tree and the o,ther is an animal. Then why is their second name the same?

In short, we do not think about the uniqueness of the second part of the binomial (the species epithet) but about the uniqueness of the binomial itself (the genus and the species epithet). Thus, the unique _binomial_ of mango is _Mangifera indica_ and the unique _binomial_ of bee is _Apis indica_. For more detail, see this question.

To complicate matters slightly, plants and animals are governed by different nomenclatural codes. So it is possible for a plant to have the exact same binomial as an animal. These are called "hemihomonyms." For more detail, see this question. However, a plant cannot have the same binomial as another plant, and an animal cannot have the same binomial as another animal.

In this specific case, the authors probably chose to give both species the epithet _indica_ because they are associated with the Indian subcontinent, which is the root of that word.