Summary. The composition of the defensive secretion of larvae of 8 Nematinae species is reported. 7 derivatives have been identified: benzaldehyde, (E)-2-hexenol, (E)-2-hexenal, (E)-4-oxo-2-hexenal, geranial, neral and cis, trans-dolichodial.Various types of defensive mechanisms have been reported for Tenthredinidae larvae 3. In particular, many larvae of the Nematinae subfamily possess well-developed medio-ventral abdominal glands 4. These glands are eversible and emit an odoriferous, sometimes pungent, secretion that efficiently repels ants 5. Since no data on the chemical nature of the active compounds of this group of insects were available, we decided to analyze the larvae secretion of 8 European Nematinae species. The larvae were collected in Belgium on different host-plants which are listed in the table. The secretions were obtained by gently pinching their abdomen. This induces the eversion of the glands, and droplets became visible on their surface. These droplets were then collected on bits of filter paper and stored in pentane or hexane at -30 ~ It was not possible to collect in this way the secretion of the small galicolous larvae of Pontania proxima from which total extracts in pentane were prepared. These solutions were analyzed by capillary GLC on 2 different liquid phases 6. The volatile components identified are listed in the table. Identification of benzaldehyde in Pontania proxima and Nematus crassus as well as of geranial (1) and neral (2), the stereoisomers of citral, in Nematinus luteus, is based on the odor and the retention times in comparison with authentic reference compounds (mixed injection in capillary GLC on 2 different stationary phases6). Retention times comparison shows that this dialdehyde is also the major derivative of the secretion of Nematus spiraeae.
Construction d'un outil d'évaluation de la qualité des actions d'accompagnement pédagogique. Synthèse d'échanges et d'analyse de pratiques professionnelles en Communauté française de Belgique
volition, entre motivation et cognition : quelle place dans la pratique des étudiants, quels liens avec la motivation et la cognition? », Revue internationale de pédagogie de l'enseignement supérieur [
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