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The hibernation dynamics of Oryzophagus oryzae (Costa Lima) (Coleoptera, Curculionidae) was studied in a bamboo stand, in Eldorado do Sul district (30° 02′ S, 51° 23′ WGR), RS, Brazil. From February 1990 to February 1991, a total of 12057 insects were sampled in the litter of the study area (80 m × 2 m), following a stratified random sampling programme. Four major phases were recognized in the phenology of the hibernating population: (1) a period of arrival at the hibernation site (February–March); (2) a settling period at the site; (3) a period of departure from the hibernation site (August–November); and (4) a residual period. Thus, diapause lasted about 7–8 months. The total mortality rate was 42% and a high rate of infection by Beauveria bassiana (Bals.) Vuill. was recorded among the dead insects (43%). Microclimatic profiles showed a narrower interval of variation of the air temperature and relative humidity in the bamboo litter than in the open field, hence characterizing the site as a refuge for hibernation. The concentration of high densities of hibernating adults in small areas, the long duration of diapause and the high natural occurrence of B. bassiana make the hibernation period a very appropriate and recommendable time for control of this weevil. |
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