ヨコヅナサシガメ Agriosphodrus dohrni Signoret に関する生態学的研究 II : その周年経過及び幼齢期の記載

The Reduviid, Agriosphodrus dohrni Signoret, has but one generation a year. The duration of each developmental period is : 40 days for the eggs, 24 days for the first stage nymphs, 18 days each for the second and third, 32 days for the fourth and about 7 months for the last stage nymphs. In the life-history studies conducted in the field, the entire developmental period (egg to adult) was never less than 11 months. Variations in the length of the developmental period appear to be due primarily to fluctuations in the length of the nymphal life which is very much influenced by the amount of food. This species spends the winter in the fifth nymphal stage. From December to February in the following year the nymphs do not take food. At room temperatnres the longevity of the adult stage ranged from 17 to 73 days. Copulation is performed in such a position as the male lying dorsally to the female. The male grips his mate with all of his legs, and his rostrum rests on the pronoturn of the female. Oviposition occurs in late May. The newly hatched nymphs do not move away from the ootheca for three to seven days. At night or on the rainy days the nymphs would aggregate themselves in a certain favourite habitat. This habitat is changed several times according to the different conditions of the season. The overwintering habitat is restricted to such a place as having the maximum high temperature at night. In all the nymphal stages this Reduviid has its favourite habitat, where a number of individuals are aggregating during night as given in my first report. This habit may be regarded as a peculiar and well developed one of the types among insect aggregations.

1. 第1報に引続き, 本稿に於ては, ヨコヅナサシガメ Agriosphodrus dohrni Signoret の周年経過及び卵・幼虫の特徴の簡単な記載につき報告する. 2. 年一世代を繰返し, 経過は第1図のようであるが, その幼虫期の全期にわたり,一定の集中場所をもつ集団をつくることが見られる. 3. 各齢期の長さは, 卵期間40日, 幼虫期間は第1齢幼虫で24日, 第2齢幼虫18日, 第3齢幼虫18日, 第4齢幼虫32日, 第5齢幼虫約7ヶ月, 成虫は実験室での飼育例ではあるが17～73日であつた. 本種は第5齢の幼虫態で越冬する.