-εω verbs in Herodotus.—a. Hdt. generally leaves εο, εω, εου, open, except when a vowel precedes the ε, in which case we find ευ for εο (ἀγνοεῦντες). In the 3 plur. -έουσι is kept except in ποιεῦσι. For -έ-εο in the 2 sing. mid. we find έ-ο in αἰτέο. εε, εει, in stems of more than one syllable, are usually uncontracted in the Mss., but this is probably an error. δεῖ
b. In the optative Hdt. has -έοι after a consonant, as καλέοι, but -οῖ after a vowel, as ποιοῖμι, ποιοῖ.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].