Periodicity and individualism in the granary weevil, Sitophilus granarius (L.) (Coleoptera, Curculionidae). A contribution to the dispersal behavior of stored-product pests
1994
Stein, W. (Giessen Univ. (Germany). Inst. fuer Phytopathologie und Angewandte Zoologie. Vorratsschutz)
In laboratory experiments, the behavior of the granary weevil, Sitophilus granarius (L.), was investigated under the special aspect of dispersal of this species. The results, too, should demonstrate possible changes in the behavior during the life time of the adults and differences between single specimens of the same population. The most important results are: 1) The running activity increases shortly after emergence but then it decreases again slowly till the end of life. 2) The fitness of the weevils declines during the life time continuously. 3) A dispersal phase exists in the first days after emergence. If a dispersal is prevented artificially for 12 or 20 days, only a small number of weevils still leaves the substrate (wheat), thus demonstrating the end of a dispersal phase. 4) The feeding activity is nearly similar during the whole life. 5) A few days after emgergence, unmated females begin to produce typical egg-laying holes in the wheat kernels. This behavior exists nearly unchanged during the whole life time. 6) The negative phototaxis of the first days after emergence decreases during the next days while the positive phototaxis increases. In older weevils, however, the reaction is again reverse. 7) Within a population, considerable differences exist between single specimens in respect to running activity, feeding activity, and phototaxis. This results in an occurrence of 'pioneer specimes' which have special importance for the dispersal of the species and for a foundation of new populations
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