The distribution, biology and ecology of Euphranta connexa (Fabr.), a tephritid fruit fly attacking the seeds of the perennial herb Vincetoxicum hirundinaria Medicus (Asclepiadaceae), is described based on observations in Sweden, Finland and Denmark. The female oviposits in developing fruits, where the larva subsequently feeds on the immature seeds. The insect occurs in most places where the host plant grows, often attacking close to 100% of available fruits. Usually one, but sometimes two or more larvae leave the fruit in late summer to pupate in the soil. There is one generation per year. Several parasitoid species attack E. connexa larvae, of which Scambus brevicornis (Gravenhorst) (Ichneumonidae), a highly polyphagous species, is most common and Bracon picticornis (Wesmael) (Braconidae) second most common. none