Notes on the parasitoid fauna of the serpentine leafminer Liriomyza trifolii(Burgess) (Diptera : Agromyzidae) in Okinawa, southern Japan

Parasitoid fauna of the serpentine leafminer Liriomyza trifolii (Burgess) w as surveyed in Okinawa Is., Miyako Is. and Ishigaki Is. in southern Japan f rom November through December 1997. A total of 12 species of parasitoids we re recorded as natural enemies of L. trifolii; including one Braconidae, on e Eucoilidae, two Pteromalidae, and eight Eulophidae (7 genera). All domina ting species were members of the Eulophidae. In the field, Neochrysocharis formosa was the most dominant species among the three islands, and the seco nd most dominant species was Hemiptarsenus varicornis in Okinawa Is., Neoch rysocharis okazakii in Miyako Is. and Chrysocharis pentheus in Ishigaki Is. On the other hand, in a vinyl greenhouse, the dominant species were H. var icornis and N. formosa in Okinawa Is., and N. formosa and N. okazakii in Is higaki Is. Sex ratios of the three main parasitoid species, N. varicornis, C. pentheus and N. okazakii, were nearly 0.5 for the three islands. However , the sex ratio of N. formosa was extremely female biased 0.996 in Okinawa Is., 0.86 in Miyako Is. and 0.97 in Ishigaki Is. These facts indicate that both sexual (arrhenotokous) and asexual (thelytokous) forms of N. formosa o ccur sympatrically, and the asexual strain predominated in populations of N . formosa.