コシアキトンボ Pseudothemis zonata (Burm.) の生活史の研究 : I. 成虫期の生態
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概要
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During the summer of 1966, a study of Pseudothemis zonata (Burm.) was made by the author at a shaded pond "Chi-araino-ike" at Mejiro, Tokyo. This paper deals with the biology of the adult dragonflies. From the ultimate larvae which were collected from the pond and reared in my laboratory, 120 adults were obtained (Fig. 1-1). These were marked individually and released from the laboratory (ca. 360m apart from the pond) or from the pond side in order to trace their behaviour in field. Observations were made both of the marked and the unmarked insects. Following results were obtained : (1) Sex ratio ♂/♂+♀ of reared insects was 0.458. (2) Of 55 marked males 6 individuals (11%) were seen at the pond between 9-30 days after release. These were mature insects with whitish basal abdominal segments. Therefore 9 days may be enough for maturation in mid-summer. The reproductive period may be 10-25 days and post-reproductive period may last up to 30 days or more (Fig. 1-2). (3) No marked female was observed at the pond. (4) The behaviour of immature insects was observed at a sunny place 260m apart from the pond (Fig. 2). One male and one female stayed on this site for 2 successive days. The male was on the wing without alightening at most 25 min. whereas the female at most 19 min. (5) Vertical separation of flight space above the water was observed among reproductive males, young males and females (Fig. 3) and the horizontal separation of the pond was found between males for reproduction and those for feeding (Fig. 4). (6) Pattern of reproductive flight was found to undergo changes with age : beginning with localized type at the sunny open water (see Fig. 4) towards marginal type along the shaded pond boundary (Fig. 5). (7) Dual flight of males in combat was analyzed and divided into 3 phases ; (1) pursuit-, (2) display- and (3) final phase, and then discussed on these phases comparing with those of some other Libellulids. (8) On June 27th the behaviour of a marked male (17 days old) was observed to be keeping his territory ; the duration being about 3 hours expelling other males for 26 times (15 times by dual flight), he also mated once and perched for 14 times. Duration of resting was 34min. in accumulation. (9) Copulation took place on flight above the pond water, the duration being 5-7 seconds. The oviposition follows immediately after mating by the detached female beside the guarding partner. (10) Oviposition was made on wet surface of floating objects such as dead branches, sticks of bamboo and the similar materials (Fig. 7 above). (11) If not disturbed by other males, females do oviposite more than 1000 eggs adhering the eggs on the object by touching the tip of abdomen, 7-9 eggs being issued on each flick (Fig. 7, below). (12) To evaluate preferency for territory making we assumed most balanced territory number (Tm) in an area and actual number of flying males (N). Then the value of a particular area can be given by N/Tm. The area A was found to have highest value in mid-summer. The sequence was A (1.3-3.0)>B (1.0-2.0)>D (0.3-1.0)>C (0). (13) Resting site selection in day time was recognized (Fig. 6-1, 2). For overnight rest some insects choiced a spot near the top of dead slender (2mm or less in diameter) twigs sheltered by dense foliage 2-5m above water.
- 日本昆虫学会の論文
- 1967-04-10