Reference in Pi. I. 1.55 referring to Amphitryon's sons, viz. Herakles and Iolaus (grandson), and thus the Herakleia and Iolaia at Thebes. According to the scholiast Herodotos won one or both of these events.
Honorand of Pindar's first Isthmian Ode. I follow Farrington (2012), p. 116 note 264 for the dating, based on the dating of the ode and perhaps the political/military career of Herodotos' father Asopodoros. As for Herodotos' victories, much depends on the reading of line 11 of the Ode and scholiastic remarks - cf. Farrington (2012), p. 116-7 note 265 for discussion. He perhaps won only one Isthmian victory (viz. one of the six mentioned in line 11, for which the ode was written) and some less well known contests enumerated from lines 52-9, where it is also suggested Herodotos won with the chariot. - PK