On the Altitudinal Variation of Age Distribution and Development of Ovaries of Overwintering Arrowhead Scale, <i>Prontaspis yanonensis</i> KUWANA at Mt. Unzen, Nagasaki Prefecture

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  • 雲仙におけるヤノネカイガラムシの越冬形態の垂直的変化
  • ウンゼン ニ オケル ヤノネカイガラムシ ノ エットウ ケイタイ ノ スイチョクテキ ヘンカ

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Altitudinal distribution and variation of such biological characters as age distribution, mortality in each stage and the development of ovaries of adult females of overwintering populations of arrowhead scale, Prontaspis yanonensis KUWANA collected from nine stations which were arranged along the western and eastern slopes of Mt. Unzen, Nagasaki Prefecture were studied in March of 1953.<br>The altitudinal distribution of arrowhead scaleranged from the seashore to 280m above the sea level. On the upper part of this range, it was observed that the population density of arrowhead scale become lower and other scales such as Pinaspis strachani and Lepidosaphes gloverii appeared instead.<br>The age distribution of arrowhead scale from each stations were compared. Almost of all the living scales were immature or mature adult females. The number of living individuals per one leaf was 10 to 20 at the stations which ranged between 20 and 150m in altitude and less than 10 individuals at the stations between 150 and 280m in altitude. At the high altitude stations, overwintering stage was restricted in adult females only. On the contrary, some of the young larvae of both sexes were overwintered at the low altitude stations. The most survivals of the overwintering populations were consist of females. The percentages of survival of each stages were 5 to 20% among young larvae and 50 to 90% among immature or mature adult females. Any significant differences of the percentage of the survivals among stations were not observed.<br>The development of ovum was examined by the dissection of ovaries of adult females. More of the developed ovum were found in the samples from the lower stations than that of higher stations. The number of developed ovum per one female was generally proportional to the altitude of collecting stations.

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