Temporal Decrease in Clutch Size of the Herbivorous Lady Beetle Epilachna niponica (Coleoptera, Coccinellidae)

概要

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Temporal changes in clutch size of Epilachna niponica were monitored over a 5-year period in two local populations at study sites A and F in northwestern part of Shiga Prefecture. The average clutch size at site A was significantly larger than that at site F. A seasonal decrease in clutch size was detected in both of the populations. In particular, at site F clutch size late in the season was approximately half of that early in the season. However, the clutch size did not significantly differ between the two populations when compared for each half-monthly period. A temporal decrease also occurred in the laboratory. The laboratory experiment revealed the age-dependent reduction in clutch size for individual females. The significant inter-population difference in clutch size was accounted for by the differential length of oviposition period in the two populations : population F with a longer oviposition period had a higher proportion of smaller clutches deposited late in the season, compared with population A which had a shorter oviposition period. Average number of ovarioles of individual females did not significantly differ between the two populations, and coincided closely with the clutch size at the beginning of the season.
日本昆虫学会の論文
1991-12-25