1959 Volume 3 Issue 1 Pages 1-6
In the zone of three generations of rice stem maggot, Chlorops oryzae M., the first generation maggots feed several developing leaves and pupate before the formation of young ears of host rice plants, but the second generation maggots feed the developing leaves and young ears, then they pupate after heading of host plants.
Therefore, in the first generation the maggots grow under homogeneous condition on all varieties of rice plants, but in the second generation they grow under various conditions on host plants since the dates of heading vary in different varieties.
Author investigated the larval growth of the second generation on various varieties and on hosts sawed on various dates. And he considered the difference of the larval growth of the first and the second generations.
The results obtained are summarized as follows.
1. The maggots of the second generation were reared on the same young stage of rice plants as in the first generation, but the larval growth in the second was later than in the first.
2. In the second generation, the larval growth in the eary stage was closely related to development of the young ears. Therefore, the growing processes of larvae were varied with heading dates of host varieties.
3. Dates of pupation and fly emergence were, too, varied with heading dates of host plants, but the duration from heading to pupation becomes gradually shorter as the heading dates becomes later.
4. In Norin no.1, early variety, about 20 per cent of maggots pupated on the nineth day after heading date, but thereafter the pupation almost stoped till the beginning of September when the maggots in the middle varieties began to pupate. From this fact, it is reasonably considered that the pupation might be inhibited in the middle and late of August.
5. Shirogane, the susceptible variety to this maggot, was sawed on various dates from early to late, and the maggots of the second generation were reared on those rice plants.
The growth of larvae was closely related ot the date of sawing the seeds, that is, the date of heading, and the larval growth and pupation became later as the date of sawing became later, but, as written in III, on the rice plants sawed on the last date, 3rd of July, the larvae grew to the third instar without feeding the young ears.
From this fact, author inferenced that the growth of the early stage of larvae might be inhibited in a certain stage of host rice plant.
6. Author discussed that inhibition of growth in the early stage of larvae and inhibition of pupation after larvae have riped in eary varieties were considered to be the main reasons why the second generation maggots in the fields require a longer duration for their development than the first generation.
