Article révisé par les pairs
Résumé : Phenolic glucosides from willow leaves are used by Chrysomela vigintipunctata larvae as precursors of salicylaldehyde produced in the defensive secretion. When these larvae were fed on different Salix species with high to moderate phenolic glucoside content (S. purpurea, S. myrsinifolia, S. fragilis), their defensive secretion mainly contained salicylaldehyde and only traces of other constituents (benzaldehyde and phenylethanol). The volume of SeCretions was reduced in larvae fed on host plant with low to very low phenolic glucoside content (S. caprea). Salicylaldehyde remained the predominant constituent in most secretions, but in some, (Z)-3-hexen-1-ol, benzaldehyde and phenylethanol, appeared as major constituents besides salicylaldehyde. Quantitative assessments demonstrate that these compounds did not compensate for the reduction in salicylaldehyde as compared with the amount produced when fed on Salix with high phenolic glucoside content. The results are discussed in terms of sequestration ability, defence, and host range observed in nature.