Abstract.1Delia flavifronsZetterstedt (Diptera: Anthomyiidae) visits flowers ofSilene vulgaris(Moench) Garcke (Caryophyllaceae), where the adults feed, mate, lay their eggs, and the larvae feed on developing seeds. The objective of the study was to examine how an ovipositing female fly assures a food resource for her progeny.2Ovipositing females preferred young, non‐pollinated flowers over older pollinated ones. The flies did not pollinate the flowers and survival of the larvae depended on the flowers being pollinated by moths.3Flowers containing fly eggs were pollinated more often than expected from chance, probably as a result of both flies and moths visiting particular flowers.4Eggs were laid singly, and multiple oviposition occurred randomly. Although most eggs hatched, only about half produced larvae that made their way into the fruits. As a result, the probability of competition arising from multiple oviposition may be reduced to such an extent that selection does not favour females that avoid flowers with conspecific eggs.5Moth larvae of the noctuid genusHadenaalso feed on the seed pods ofS. vulgarisand will kill any fly larvae they encounter. However, there was no deviation from random oviposition by the flies in relation to eggs laid by the moths, but the competitively weaker fly usually started to lay eggs towards the end of the moth's egg‐laying period.6The relationship betweenDelia flavifronsandSilene vulgarissuperficially parallels that for known pollinator/predator systems, but floral adaptations to hypothetically pollinating flies seems not to have taken pl