ECOLOGY OF PLA TYGASTER MA TSUTAMA AND INOSTEMMA SEOULIS (HYMENOPTERA : PLATYGASTRIDAE), EGG-LARVAL PARASITES OF THE PINE NEEDLE GALL MIDGE, THECODIPLOSIS JAPONENSIS (DIPTERA, CECIDOMYIIDAE)

概要

論文の詳細を見る
Platygaster matsutama and Inostemma seoulis and their host, Thecodiplosis japonensis, are univoltine. Adults of both parasites emerge from hibernating host puparia ; the emergence periods are mid-May through mid-June for P. matsutama and early June through mid-July for I. seoulis. The females of P. matsutama oviposit into host eggs, those of 1. seoulis either into newly hatched larvae or into eggs just prior to hatching. The average numbers of ovarian eggs per female were 1,569 and 555 for P. matsutama and I. seoulis, respectively, and the female : male sex ratios for adults of both species collected in field emergence traps were 38 : 62 and 60 : 40, respectively. The parasites mate and oviposit during the day, and rest on the undersides of leaves of broadleaved plants at night. In both parasites, development is monembryonic. Whereas P. matsutama has only one larval instar, I. seoulis has two. In P. matszttama, the duration of the pupal stage averaged 31.6 days at a laboratory temperature of 20°C. In cases of symparasitism, adults of only P. matsutama emerge ; 1. seoulis dies in the first stadium. In cases of superparasitism by P. matsutama, all individuals reach adulthood, but in I. sea&is only one adult can emerge from a single host puparium.