AbstractA resume is made of the major sequences of egg-laying behaviour, both in nature and on stored seeds, of the bean weevil. An experimental analysis of the role of the ovipositor in the act of egg-laying is then undertaken by simple techniques. It is observed that an important stimulus, with respect to this, is mechanical in nature: resulting from contact between the setae of the ovipositor on the one hand, and the seed and the "ground" on the other. Simply suspending the seed instead of leaving it lie on the cage bottom, suffices to reduce egg-laying and production significantly. Examination of egg-laying, when the substratum furnished is a trellis with suitable sized mesh, shows that an important aspect of the mechanical stimulus is in its concentrical character, i.e., the fact that it is applied to a greater number of setae all around the ovipositor. The result enables us to understand better the behaviour in nature, where there is a boring of the bean pod followed by egg-laying inside that pod through through the hole made. In the course of the paper some connected problems are evoked: - The relationship between egg-laying and production; - The more or less necessary character of the succession of the different sequences in egg-laying behaviour. Existence of intermediary cases, between individuals which can lay eggs only in the pod and those laying in the apparent absence of any stimulus, particularly stimuli connected with the bean; - Links between the phytophage and its host, remarks on the apparently unfavourable peculiarity of laying a great number of eggs in the same place, the possible consequences with respect to population dynamics.
