The biology of Euphranta connexa was investigated to assess its potential as a biological control agent for introduction in North America against the invasive weeds Vincetoxicum rossicum (Kleopow) and V. nigrum (L.) (Apocynaceae). A range of temperatures suitable for development was determined for the pupal and egg stages of E. connexa. The pupa is the overwintering stage of E. connexa and does not exhibit a diapause, but undergoes a cold induced quiescence. The relationship of temperature to pupal developmental was investigated and did not differ among insects from sites over a range of altitude of 1300 m, indicating E. connexa may not be locally adapted. When adult female E. connexa emerged from pupae they had not developed eggs but 10 to 15 days later they had a full complement of developed eggs. Mating of E. connexa did not affect the egg load of females but egg load was reduced in females that had spent longer as pupae in cold conditions. There was evidence that females could reabsorb previously developed eggs. In surveys for larval and larval-pupal parasitoids of E. connexa infested seedpods of V. hirundinaria from three countries, there were a total of 1599 parasitoids from eight Hymenoptera families,and most parasitoids were Braconidae. Prior to the survey, the fruit midge, Contarinia asclepiadis (Diptera: Cecidomyiidae) was considered rare, but it was found in seedpods from all collection sites in Switzerland and infested about 9.2% of seedpods at two localities in 2013. Of 13 parasitoid morphospecies found in the survey, two braconid and one ichneumonid morphospecies were frequent and were parasitoids of E. connexa, three platygastrid morphospecies were probably parasitoids of C. asclepiadis, and three morphospecies were probably hyperparasitoids. The thesis research will allow development of effective methods for studying impact and host range of E. connexa, studies that are required to assess the potential as a biological control agent against V. rossicum and V. nigrum.