Question for Illustration about Peloponnesian War

[Commilito]

At what date exactly did Greek light troops begin to adopt the Celtic/Italian style body shield? I know that later in the Hellenistic period light troops fought with them as skirmishers who were known as Thyreophoros.

but would it be okay to show light troops equipped with these shields in the late stages of the war? (Sicily onwards).

thanks.
ill post pictures of my work within the week.

happy 4th of july to all fellow americans!