1. The role of 1st and 2nd ganglia on the oviposition in Bombyx mori and Antheraea pernyi was investigated with extirpating either of these ganglia.
2. Dissected at the front area of the head, the 1st ganglion could be easily removed.
3. By the removal or the injury of the 1st or 2nd ganglion in the moth of Bombyx, the oviposition of almost all moths were checked with a few exception of those laying a smaller number of eggs.
4. The similar experiment in A. pernyi resulted in a complete checking the oviposition without exception.
5. In both insects, eggs laid by moths which had been extirpated the 1st or 2nd ganglion in pupal stage were greater in number than those operated in the same way in moth stage, but were far smaller than the normal.
6. The absence of the 2nd ganglion causes some difficulties in oviposition as that of others does. The present authors suggested that the 1st ganglion controls primarily the oviposition by its nervous action in Lepidopterous insects.

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A comparative study on the percentage of appearance of cytoplasmic and nuclear polyhedrosis in the silkworm reared at University of Tokyo and Shinshu University (Ueda, Nagano Prefecture) based upon the probable difference in the quality of mulberry leaves grown at the two respective places, using several resistant and susceptible strains and their hybrids, was made. The results obtained are summarized as follows:
1. In the experiments conducted on the spring rearing, in which the low-temperature treatment (5°C, 24 hours) was given to the 5th instar soon after ecdysis, cytoplasmic (mid-gut) polyhedral diseased larvae appeared less at Ueda than at Tokyo.
2. In the case of summer rearing in which low-temperature treatment was not applied, a result similar to the above was obtained, i.e. the number of larvae affected by mid-gut polyhedral disease were less at Ueda than at Tokyo.
3. The percentage of mid-gut polyhedral diseased larvae induced by the low-temperature treatment in the summer rearing was higher at Tokyo than at Ueda.
4. The larvae reared first at Ueda for the 1st and 2nd instar and then at Tokyo from 3rd to 5th instar, showed an intermediate value of mid-gut polyhedrosis between those reared at Ueda and at Tokyo, respectively from the 1st up to the 5th instar.
5. From these results, it may be plausibly thought that some environmental factors, in this case the quality of mulberry leaves, markedly influence the appearance and induction of the cytoplasmic polyhedrosis in the silkworm.

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Studies on the induction of nuclear and cytoplasmic (mid-gut) polyhedral viruses utilizing nitrogen mustard, X-rays, ultraviolet rays have been carried out in the silkworm with a few susceptible and resistant races, hybrids and od oily mutant.
As numerous diseased larvae in the 5th instar appeared typically displaying the formation of polyhedral bodies in the cytoplasm of cylindrical cells in mid-gut by the nitrogen mustard treatment (feeding and injection) in the 3rd, 4th and 5th instars, so it may be concluded that the cytoplasmic polyhedral virus can be induced by the nitrogen mustard treatment. The nuclear polyhedral bodies observed in a hybrid treated by nitrogen mustard showed tetragonal configuration different from normal polyhedra, which are hexagonal.
The phenomenon of the induction of both the nuclear and cytoplasmic polyhedral viruses was not recognized in the experiments of X-rays and ultraviolet rays treatments.

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Studies to investigate the relationship between the occurrence of the cytoplasmic polyhedrosis (mid-gut polyhedral disease) and the rearing seasons (spring, summer and late autumn) in which the quality of mulberry leaf was thought to be different, have been made in these three years (1955-1957). These experiments have been carried out both with no treatment and treatment with low temperature (5°C, 24 hours) of the 5th instar larvae soon after ecdysis using numerous races, hybrids and biochemical mutants.
In the spring rearing, much less mid-gut polyhedral diseased larvae occurred than in the summer and late autumn seasons. The mid-gut polyhedrosis showed less occurrence in summer rearing than in the late autumn. The same tendency was observable in the induction experiments of the mid-gut polyhedral virus by the low temperature treatment.
It may be plausibly thought that the main factor controlling the occurrence of the mid-gut polyhedrosis is the quality of mulberry leaf. But several other environmental factors like temperature, humidity etc. should not be ignored. The quality of mulberry leaf given to the larvae before the low temperature treatment has the influence upon the induction of the mid-gut polyhedral virus.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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