I'm not native english speaker, but I have a feeling "on insects" migh do it.

It accepted I'm a specialist in wines.

It'd be less awkward to say "wine specialist" or "insect specialist." Or even better: "sommelier" or "entomologist."

ou em português de Portugal: escanção

Professions, in English, just require the indefinite article, whereas in Portuguese it is not required but understood. If the definite article is required in English, it is most certainly required in Portuguese.