マイマイガの水分量, 脂肪量, 酸素消費量およびグリコゲン量の季節的変化

抄録

The so-called gypsy moth, Lymantria dispar, is one of the most serious pests in the forest and orchard. In Japan, although more than 80 different species of plants are given in the list of those fed upon by this insect, especially this caterpillar feeds on foliages of apple, pear, Japanese apricot, cherry, persimmon, loquat, Japanese larch, Japanese alder, painted maple, Japanese elm, Japan poplar, goat willow, oak and mulberry trees, and it also attacks the foliage of some garden plants. The moths pass the winter in the egg stage. There is but one generation of the insect each year. The eggs laid in masses are covered with a coating of hair and are about the color of chamois skin. The larvae of this insect begin to appear from late March to mid-April in warm regions. They become full-grown during the first half of June and spin a very loose light cocoon on the trunks of trees and other near-by objects. Within this they change to a dark-brown pupal stage in late June. Lastly, the moths begin emerging during one or two weeks after their pupal development. The female deposits her eggs on various objects. Eggs are laid in late June or July and do not hatch until the following spring. As mentioned above, considerable knowledges have been accumulated on the importance and life history of this species by the present time, however, the physiological aspects of the moth have scarcely been advanced. From these reasons, it seems reasonable to clarify in this article on the oxygen consumption, water, fat and glycogen contents during egg, larval and pupal growth in the gypsy moth.
The gypsy moths used in this study were hand picked in the egg stage from the cherry or oak trees and a large extent of them was brought into laboratory. In this case, the rearing was done in a cabinet at a constant temperature unless otherwise indicated. The fat content was thus determined using Soxhlet apparatus. for 24 hours as the total ether-extractable material expressed as a percentage of the live weight of the gypsy moths. The amount of oxygen uptake was also measured in Warburg constant volume respirometer over periods of one hour at a temperature of 25°C. Of course, carbon dioxide produced during the experiment was absorbed by 0.2 ml. 5 per cent KOH solution in the centre well of the flask. In addition, the glycogen content of the moths was recorded by means of anthrone's colorimetric determination method.
Data in the egg stage presented monthly in Table 1 show that the accumulation of more fat in the eggs is not responsible for the increment of water. Roughly speaking, as the percentage of fat increases, the percentage of water decreases regardless of the season. From the result of glycogen content in the eggs shown in sequence with the progress of seasons, it may easily be seen that a greater amount of glycogen was maintained at mid-July when the moths begin to lay their eggs, and it dropped sharply toward following year.
Water and fat contents in the various stages of moth are shown in Table 2. On this evidence, it would be more justifiable to say that although the water content of eggs during the intense cold season of winter was kept at low level, but it more increased just before the larvae begin to hatch in April. And after they attained to the larval stage, water tended to increase gradually and again reduced in the pupal development. The fat accumulation, on the other hand, was retained slightly at high level in corresponding season of winter, and then it diminished after hatching was ended. Simlarly, the sequence of fat content in the pupal growth run about the same course with the tendency of larval stage.