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On the bionomics of Itoplectis narangae (Ashmead) : (Ichneumonidae, Hymenoptera)

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概要 The present work was carried out in the field and laboratory for two years in order to clarify the bionomics and the mass production method of Itoplectis narangae for the future use as a controlling a...gent against the major rice pests. The results are summarized as follows: 1. This species develops 4 or 5 times a year from the middle of May to early December and hibernates as the final instar larval stage within the host body. It seems that the searching zone in the paddy field is closely correlated to the microclimate and that the lower part of rice plant is not searched by this species. 2. The larval stage ends at the fifth instar and each instar can be discriminated by the width of head capsule. The developmental period varies according to the rearing temperature and host species. The average developmental period on the host pupa of Galleria mellonella under the constant temperature condition of 25℃ is 14.0 days in male and 14.9 days in female. The body color also varies according to the rearing temperature and black color does not develop as temperature rises. 3. The host feeding was observed during the oviposition period. It was observed that this species sucked water on the leaf of rice plant in the field and visited flowers in the carrot field to get nutrient from them. It was also observed that the species was taking honeydew excreted by the aphids on the ear of rice plant. 4. The male emerges earlier than the female. The female mates soon after emergence. 5. It seems that the oviposition is not affected by the age in days, dorsal and ventral sites and sizes of the host. 6. This species is unable to discriminate the parasitized or unparasitized host. There was no case in which more than one parasite emerged from the superparasitized host. 7. Arrhenotokous parthenogenesis is seen in this species. 8. Mature eggs in the ovaries are produced from the first day after emergence irrespective of feeding. It reaches the peak in the second day when unfed and in the third day if fed with diets. Thereafter, the o&sorption proceeds gradually and the number of matured eggs decreases. 9. This parasite is a synovigenic species. The preoviposition period is 1 to 2 days on an average. There is no difference in its reproductive capacity between the mated and unmated females. A female lays 300 eggs on an average, but the number of eggs deposited varies greatly according to the individuals. High pcsitive correlation was observed between the fecundity and the size of this parasite. The daily fluctuation of oviposition shows the continuation of increase and decrease and vice versa. 10. The number of eggs deposited increases rapidly until the sixth day after the start of oviposition and active oviposition takes place for the first 14 to 21 days and decreases gradually thereafter. More than 70 % of the total number of eggs deposited is laid for 20 days after the start of oviposition. 11. The number of ovarioles observed is ranging from 11 to 28 and about 25 % of which are formed symmetrically. It seems that the size of this species is not correlated to the number of ovarioles. 12. The longevity is shortened as temperature rises. Water is somewhat helpful to extend the longevity of this species. The parasite fed with water survived longer than that fed with honey under high temperatures. The unfed parasite survived for about 5.7-5.8 days on an average under the constant temperature condition of 25℃ while those fed with undiluted honey and water survived for 36.1 days in male and 46.8 days in female respectively. 13. When the parasite was given hosts after being withheld from hosts for 10, 15 and 20 days, oviposition behavior proceeded immediately. The o&sorption of matured eggs in the ovaries took place during the period of lacking host. IIowever, matured eggs remained in the ovaries and the reproductive capacity was still maintained even after the elapse of days indicated above. 14. The size and age in days of the host pupa affected the size of this species, and the developmental period was somewhat prolonged as the age in days advanced. 15. There was observed no morphological difference between this species reared on Galleria mellonella in the laboratory and those collected in the field, expect the relative growth affected by the size of host and other factors. 16. The insecticidal action of r-BHC, Sevin and Sumithion of the ordinary concentration on the adults of this species was remarkable while the immature stage within the host pupa was not affected at all. The insecticidal action of these three insecticides was strong in the order of r-BHC, Sumithion and Sevin. The survival of this species was not affected by talc and diatomaceous earth used as diluents. 17. The mass production is possible by using the pupae of G. mellonella. The parasitization unit was designed to facilitate the handling of parasites for the mass production.続きを見る

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登録日 2012.07.20
更新日 2021.02.05

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