[Phenotypic plasticity in insects].

Insects represent 85% of the animals. They have adapted to many environments and play a major role in ecosystems. Many insect species exhibit phenotypic plasticity. We here report on the mechanisms involved in phenotypic plasticity of different insects (aphids, migratory locust, map butterfly, honeybee) and also on the nutritional size plasticity in Drosophila and the plasticity of the wing eye-spots of the butterfly Bicyclus anynana. We also describe in more detail our work concerning the thermal plasticity of pigmentation in Drosophila. We have shown that the expression of the tan, yellow and Ddc genes, encoding enzymes of the melanin synthesis pathway, is modulated by temperature and that it is a consequence, at least in part, of the temperature-sensitive expression of the bab locus genes that repress them.