none Larvae of an agromyzid leaf-mining fly, Phytomyza ranunculi Schrank, are patchily distributed among leaflets of the host plant. This study was carried out to clarify what cue their parasitoid, Dapsilarthra rufiventris (Nees), employs in locating host-present leaflets (patch location). 1) The searching behaviour of parasitoids was apparently activated by leaf odour. 2) They more often visited damaged leaflets by recognising, probably the sight, white and linear mines produced by hosts in the leaflets. 3). The also appeared to employ as a patch-location cue the sound emitted when hosts eat the tissue within the leaflet. This speculation was supported by the fact that host-removed leaflets with play back of the sound recorded on tape attracted parasitoids. In this paper we argue that the employment by D. rufiventris females of the acoustical cue, probably heard from a short distance, as well as visual cues may serve in their exploitation of the larval population of P. ranunculi.