ズイムシアカタマゴバチ ト ズイムシクロタマゴバチ トノ ケンキュウ ホウホウ ニツイテ
On some methods used for study of the two egg-parasites of the rice-stem borer, Trichogramma japonicum ASHMEAD and Telenomus dignus(GAHAN)
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(1) The writer, researching egg-parasites of the rice-stem borer, Chilo suppressalis WALKER, has recorded the presence of the scelionid, Telenomus dignus (GAHAN), and of the three trichogrammids, Trichogramma japonicum ASHMEAD, T. chilonis ISHII and Asynacta sp. in the Matsue district. Until now, however, the last two species have been obtained only from a few egg masses of the borer.
(2) In rice nurseries, and in paddy fields into which rich plants have just been transferred from nurseries, egg masses of C. suppressalis of its first brood, which are generally deposited on the upper surface of rice leaves, can be easily discovered, and in such cases it is possible to make a considerably exact estimation of the number of egg masses and of the percentage parasitism of egg-parasites.
To record the color of an egg mass of the borer at the time of its discovery is desirable, because it changes corresponding to the embryonic development in eggs (Fig. 2A).
(3) It was emphasized that to gather host species other than the rice-stem borer was necessary for study of population ecology of T. japonicum, because this species has a wide host range.
(4) Some devices, as shown in Fig. 1, were made to obtain in the laboratory parasites from an egg mass of the borer.
(5) The following method was used to examine an egg mass, from which larvae of the borer and/or adult parasies had already got away. At first, an egg mass was dipped into about 10 per cent solution of KOH or NaOH without being separated from the rice leaf to dissolve the transparent cover by which the individual eggs were got together. Then, the eggs were disconnected one after another and observed under a binocular microscope, and classified into several kinds according to such features as shown in Fig. 2.
(6) In 1958 a method was tried to examine eggs of the borer from which larvae had not hatched yet or parasites, if any, not emerged yet. Egg masses of the borer were for a while fixed in 70 per cent ethyl alcohol just after gathered in the field. Then, eggs were separately observed under a binocular. It was possible to find the embryo of the borer without dissecting or dyeing the egg, because an egg of this species is flat and its chorion transparent (Fig. 2A). Parasites, in any developmental stage, in an egg of the borer can easily be discovered by being held to the light (Fig. 2B and C).
The Shimane Agricultural College