The Influence Of Light And Temperature On Certain Characters Of The Silkworm, Bombyx Mori

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Summary of Part I 1. There exist two kinds of silkworm eggs, the dark -colored which bear dark violet pigment within the egg serosa, and the light -colored, which have little or no pigment. 2. The production of moths laying dark-colored and Iightcolored eggs depends mostly upon light and temperature during incubation. The response is varied according to the different types of voltinism. The bivoltine and tetravoltine cause nearly all the moths to lay dark-colored eggs when incubated at temperatures above 24°C. and in the light intensity of D.S F. C., while they always produce moths laying light-colored eggs at 15°C in the dark. On the other hand, the univoltine never bring forth moths laying light-colored eggs. except that an extremely small number of them results from incubation at 15° in the dark. The embryonic period which presents a high degree of susceptibility to light and temperature lies at the time when blood cells differentiate. If the bivoltine and tetravoltine are subjected to a temperature of 15° in the dark for fifteen days, only Iightcolored　eggs result, ane! if subjected to 20℃. in the light for five　days, a greater number of dark-colored eggs is produced.　3. When eggs of the bivoltine and tetravoltine are incubated under intermediate conditions (at 15° in the light, or 20° in at the dark), and those of the univoltine are incubated at 15° in the dark, the effects of light and temperature are still recognized In the following periods. a) The earlier larval stadia (the first, second and third): If kept at 28° or 30℃. and in the light intensity of about 0.5 F. C., the larvae turn out, for the most part, into moths laying dark-colored eggs, and if kept at 20° in the dark, more moths laying light- colored eggs develop. b) The later larval instars (the fourth and fifth) and the pupae become more frequently moths laying light-colored eggs under high temperature and light than under low temperature and darkness. 4. The effects of light and temperature during incubation and the earlier larval stadia, upon the production of dark-colored and light-colored eggs are enumerated as follows :-a) If incubation is performed at 20℃., the light intensity above 0.0095 F. C., or at 15℃., the light intensity above 0.0136 F. C. favors the production of moths laying dark-colored eggs. The number of light-colored eggs increases as the light intensity decreases within the mentioned intensity limits. During the larval period the lower light intensity limit is about 0.077 F. C. b) Longer wave-lengths of light than 5500 A have no effect upon the production of dark-colored eggs, likewise in darkness, while shorter wave-lengths than this show a distinct effect upon it, as the white light does. c) Thirteen hours or less exposure to daylight results in a nearly equal number of moths laying light-colored eggs as in continuous darkness. Above fourteen hours, the longer exposure produces the more moths laying dark-colored eggs. During incubation, at a temperature above 20°, more than sixteen hours exposure, and at 15°, more than eighteen hours exposure, and during the larval period. more than eighteen hours exposure result in the same number of moths laying dark-colored eggs as continuous light causes. 5. Though the batch of eggs produced by a silkworm moth is, as a rule, uniform in color, mixed hatches, dark- and Iight-colored are met with. They occur; a) when the bivoltine and tetravoltine are incubated under intermediate conditions or the univoltine at low temperature and in the dark; b) when the pupa is kept at high temperature and in the light, presumably because these conditions affect the final deposits and make them light-colored. 6. Small color variations occur both in the dark -colored and the light -colored; a) when the pupae are subjected to a high temperature (30°) in the case of the dark-colored, or to a low temperature (20°) in the light-colored, more intensive egg color is produced; b) if the eggs to be darｋ-colored arc kept at 20° for two or three days after laying or those to be the light-colored are kept at 13℃. for about ten days after laying, the intensity of egg color becomes exceedingly strong, the farther the divergence from that temperature, the weaker the egg color grows within the range 11° to 30℃. 7. Either the dark- or light-colored can be hibernating or non -hibernating eggs. The occurrence of non- hibernating eggs out of the dark -colored and that of hibernating eggs out of the lightcolored does not depend upon light and temperature during incubation, but upon the following conditions; a) Tn the bivoltine and univoltine, more hibernating eggs result if the pupa is kept at 30℃. than at 20°. This is reversed in the tetravoltine. b) When the eggs are subjected to 13° for fifteen days immediately after laying, more hibernating eggs are produced than when kept at 25° for two days or at 13° for more than twenty days. c) In the bivoltine and univoltine, most favorable conditions give about 10 per cent of nonhibernating eggs out of the dark-colored, and more than 50 per cent of hibernating eggs out of the light-colored. It is possible in the tetravoltine to make all the dark-colored eggs non-hibernating, while the light-colored do not hibernate more than an exceedingly small number in any case. 8. Hibernation of the silkworm eggs depends upon two different factors, i.e., the first hibernation substance and the second hibernation substance, as I have designated them ;-- a) The first substance is affected most strongly by light and temperature during the incubation period, but slightly in the larval and pupal stages, while the second substance is influenced by temperature only, during the pupal stage and after laying. b) The first substance is uniformly distributed to all eggs laid by the same moth, in contrast to the second substance, which differs in amount not only in different moths but also in different eggs within the same batch. 9. Egg color, dark or light, is determined by the amount of the tirst hibernation substance. The larvae provided with a definite amount of the substance turn into moths laying dark-colored eggs, but under that limit they give light -colored eggs. The embryonic stage and earlier lan-al stadia are called by the present author an anabolic period for the substance, while the later larval stadia and the pupal stage are designated as a catabolic period. 10. Hibernation of both dark- and light-colored eggs is governed by the amount of the second hibernation substance. This substance is increased in amount during the pupal per iod by means of high temperature. In the case of all races experimented with-during the first or days following egg laying-then, was manifested a high degree of susceptibility to the environmental stimuli. This was also true in the pupal stage in the tetravolting. In both cases the second substance may be destroyed by high temperature. 11. The first hibernation substance has a great connection with hibernation of eggs in addition two the egg color. The second hibernation substance also controls, besides the hibernation, the egg color variation. 12. Three types of voltinism are distinguishable as regards the amount of the first and second hibernation substances. Some small variations are met with among different races of the same type of voltinism. Summary of Part II 1. The occurrence of the three-molter out of the four-molting races is influenced by light and temperature during incubation in the following ways, a) It occurs more frequently at 20°, less at 15°, with very few at 25° and 30℃, At the temperatures between 15° and 25°, darkness is more favorable than light for producing three-molters, b) At 12 hours or less exposure to light, the results are equal to those in the dark, while 15 hours or more exposure proves as effective as the continuous light. c) The rays of the wave-lengths larger than 5500 A have no inhibitory action, but those of the smaller wave-lengths have. d) From the beginning of incubation to the blastokinesis of the embryo and during one or two days after the completion of the embryo, high temperature and light are more conducive to the three-molter than low temperature and darkness. In the intermediate period from the blastokinesis to the completion of the embryo, however, light and temperature act in a directly opposite way. 2. The occurrence of the three -molter mostly depends upon light and temperature during the larval period. It varies under the following conditions. a) When temperature rises, the number of the three molters increases, more rapidly in the light than in the dark. b) Below 28℃. the rays larger than 5500 A, and above　30°, the rays smaller than that favor the production of the three-molter. c) Below 28℃. less than 12 hours exposure to light is more favorable to the production of the three-molter, while above 30°, the more the daily exposure, the larger the resulting production. d) The effects of light and temperature are greatest in the first and second stadia, less in the third, with none in the fourth stadium. If subjected to high temperature and light from the first to the third stadium, a maximum effect results. 3. The three-molters caused by light and temperature involve more males than females, representing a sex-ratio of about 80 per cent males. 4. In the hybrids between any two different races, the rate of the appearance of the three-molter is generally larger than in pure races. Racial differences were also observed. 5. The molting of insects is due to the accumulation of certain metabolic end products such as oxides. 6. The variability of the number of molts of insects is seen in two ways as shown below: a) The increase of molts is mostly caused by lack of food. b) The decrease of them is mainly dependent upon climatic influences, especially upon light and temperature.
Kyushu Imperial Universityの論文
1933-09-00

The Influence Of Light And Temperature On Certain Characters Of The Silkworm, Bombyx Mori

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Kyushu Imperial University | 論文

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