STUDY OF CUTICULAR NONVOLATILE COMPOUNDS OF ACROLEPIOPSIS-ASSECTELLA (LEPIDOPTERA, YPONOMEUTOIDEA) INVOLVED IN HOST-RECOGNITION BY THE PARASITOID DIADROMUS-PULCHELLUS AND D-COLLARIS (HYMENOPTERA, ICHNEUMONIDAE)

Behaviour of female D. pulchellus, an ichneumonid parasitizing the leek-moth, A. assectella, was studied in presence of host-chrysalids with their cocoon or naked, washed or not by several solvents. Cuticular water-soluble kairomones were involved in host recognition by this parasitoid. Washed chrysalids were poorly stimulant for female parasitoid while the obtained aqueous extracts had a strong biological activity. These cuticular kairomones not coming from the silk seemed to be an additional stimulus to the most important chemical and physical stimuli associated with the cocoon. Laboratory rearing of the parasitoid did not seem to change really its host-recognition behaviour. Reactions to A. assectella aqueous cuticular extracts of female parasitoids reared in the laboratory for 3 or 36 generations did not show significant differences. However, a metabolic change in parasitoid larvae was considered, owing to an adaptation to the host-moth rearing conditions on artificial medium. Thus, the host diet modified the parasitism rate. At last, comparison of D. pulchellus to a sympatric species, D. collaris, attacking preferently the diamondback moth Plutella xylostella showed a best adaptation of the first species to the kairomones of their common host, A. assectella.