The following records were obtained during a fortnight at the beginning of April 1949. The localities investigated were rocky shorepools below the Laboratory, and a small area at the upper tidal limit of Tamerton Lake. In addition to imagoes collected on the wing, larvae were reared from a mud sample taken from the stream bed just below the upper limit of tidal penetration. None of the Tamerton species are marine in the strict sense adopted by Edwards (1926), but those bred out are tolerant of brackish water and belong to the estuarine fauna.