A key to the Phoridae whose larvae are aquatic or semi-aquatic (hydrophilous) is provided. Megaselia humida sp. n. and M. kovaci sp. n. are described from Malaysia. M. bivesicata Schmitz andM deningi Disney are reported to be highly variable species and two synonyms are proposed, thereby both resolving the problem of the supposedly unknown male of the former and revealing that many critical couplets in Borgmeier's keys to Australasian and Oriental Megaselia are unreliable. Preliminary keys to larvae and pupae are provided.