[Study of the vertical transmission and horizontal transmission of "Drosophila melanogaster" and "Drosophila immigrans" picornavirus (author's transl)].

The contamination of drosophila eggs, of larvae of the 3 instars and of adults, was studied using several strains of P and C viruses of D. melanogaster and of iota virus of D. immigrans. The infected adults contaminated other flies if they were rich in viral particles and if the contact was long enough. Infection of the adults occurred in the presence of concentrated viral suspensions. The larvae were easily infected when they grew in contaminated media; the more sensitive stage was the first instar. Transovarian transmission was observed only in naturally infected flies propagating viruses of serotype I or III. C viruses were not hereditarily transmitted. Persistence of the Picornaviruses of drosophila populations can be explained by the additive effects of the 3 mechanisms of contamination.