Peristenus varisae spec. nov. (Hymenoptera: Braconidae) parasitizing the European tarnished plant bug, Lygus rugulipennis Poppius (Heteroptera: Miridae)

Nymphs and adults of Lygus species, mainly L. rugulipennis Poppius were collected from wheat fields in southern Finland, near Helsinki. The parasitization rate of braconid species was determined by dissection of the hosts. Parasitoids were reared from separate samples from the same fields.The parasitization rate was low, the maximum percentage occurring during the season, examined in 10-day periods, was 14%. All nymphal instars, except the first one, were found to be parasitized; the mean varied from 3% (third instar) to 6.5% (fourth instar). In adult hosts the mean parasitization rate was 2% in males and 4% in females. The percentage of parasitization in both nymphs and adults was higher in wheat bordering fields with a mixture of field bean and oats or settled areas compared with wheat adjacent to cereal or sugar beet areas. However, the total numbers of Lygus and of unparasitized specimens were higher in these surroundings. Parasitization of Lygus species in Finland appears to be too low to affect the populations. It was ascertained that the new species of Peristenus parasitized in L. rugulipennis. Its possible presence in other Lygus species was not confirmed in this study. The life cycle of the parasitoid was in synchrony with the development of the host. The Peristenus species in question did not fit in the keys to any described species and is described in this article as new to science. A key to the Peristenus species reared from Lygus rugulipennis in Europe is added. Peristenus stygicus Loan, 1973, is synonymized by the second author with P. relictus (Ruthe, 1856) syn. nov.