マメコバチを加害する労働寄生性コナダニ類2種の繁殖戦略 : I.侵入・加害様式と餌の分割利用

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Three species of astigmatid mites which infest mason bees, i.e., Chaetodactylus hirashimai, C. nipponicus and Tortonia sp., are known to occur in Japan. Two of them, C. nipponicus and T. sp. are sympatrically distributed in central and northern Japan. They are cleptoparasites of Osmia cornifrons, which is utilized as a pollinator of apples. The invasion/infestation patterns of these mites were studied through a survey conducted at 24 apple orchards in various localities during winter between 1999 and 2001. A population of O. cornifrons was reared in Sendai City, northern Japan, in spring of 1999 so as to analyse the synchronization between invasion/infestation of mites and nesting activity of host bees. As overwintering stages of C. nipponicus, phoretic and cyst-like deutonymphs were found together in the same cells, while 5 stages (larvae, protonymphs, tritonymphs, adults and phoretic deutonymph) were confirmed to hibernate in Tortonia sp. The cyst-like deutonymphs were absent in the latter species. In C. nipponicus, the percentage of phoretic deutonymphs was extremely high (up to 99.6% per host cell), while in T. sp. was lower (6.6% in total). The life type of these 2 mite species is regarded as phoretic- and dweller-like, respectively. The difference of their life types between 2 mite species are enable the partitive use of the pollen-mass stored in the same nests. The following features, regarding to the invasion/infestation patterns, were recognized. 1) Mostly, the first nests made in tubes were infested by both species of mites. The number of cells infested by C. nipponicus extended up to 9 cells, but usually the inner ones were apt to be infested. On the other hand, infested cells were found throughout nest tubes in T. sp.; 2) Distribution and numbers of dead cell contents in a nest by infestation of mites differed between 2 mite species. Only 1-3 cell contents were killed in C. nipponicus, and none killed in T. sp.; 3) Prior to feed on the stored pollen-mass, both species of mites killed hosts. However, they were able to kill hosts of which stages were from egg to early third instar larva. To kill host eggs, it was needed more than 50 adult mites. Those hosts that escaped from slaughter survived and formed normal cocoons; 4) Coinhabiting with C. nipponicus and T. sp. in the same host cell was less frequently occurred (7.1% in total). In these cells, the individual ratio of C. nipponicus was always higher than that of T. sp. The 5 overwintering stages, except phoretic deutonymph, in Tortonia sp. were not all in diapause. These stages began to develop into the next stages sooner, when new food was given under warm temperature. The phoretic deutonymphs of both mite species activated their development by clinging to host bee bodies in both mite species. The cyst-like deutonymphs of C. nipponicus developed into the tritonymphs when subjected them to the scent of host bees.
日本昆虫学会の論文
2002-12-25

マメコバチを加害する労働寄生性コナダニ類2種の繁殖戦略 : I.侵入・加害様式と餌の分割利用

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