CYCLE BIOLOGIQUE DE PISSODES NOTATUS (COLEOPTERA, CURCULIONIDAE) DANS LA REGION TOULOUSAINE (FRANCE)

The maximal emergence of Pissodes notatus (F.) adults takes place during July and August. It results from the different evolution of two populations:— a first population, whose complete development (from egg to adult) takes 11 or 12 months. This population corresponds to eggs laid after the middle of July (maximum egg laying during September). Most of the larvae having reached the third instar, it shows no more evolution during the winter; the further development takes place during the next spring, and adults emerge from mid-June to mid-July.— a second population resulting from egg laying, between February and July, of hibernated adults (maximum egg laying during April and May). The whole development being very short (2 to 3 months), the adults, corresponding to these eggs, emerge from the middle of July to the end of August.The observed differences between durations of the under-bark development (from 2 to 12 months) appear free of diapause and probably result from rates of development changing with temperature and instar.In our regional field temperature conditions, all the individuals reach finally their under-bark development approximatively at the same time, so that the adult emergence period takes place in July and August.