Reovirus-like particles and their vertical transmission in the Mexican bean beetle,Epilachna varivestis (Coleoptera: Coccinellidae)

Examination of thin sections of organs and tissues from the Mexican bean beetle, Epilachna varivestis, adults and larvae revealed the consistent presence of isometric, reovirus-like particles in the cytoplasm and rarely in the nuclei. Cytoplasmic inclusions having a dense and finely granular matrix with virus-like particles at their periphery were noticed occasionally. These inclusions were, however, very frequent in the nurse cells in the germarium of the ovariole. Virus-like particles were found in the cytoplasm of oocytes and eggs as well as embedded in the nuclei of sperm, thus suggesting vertical transmission of these particles, and explaining the 100% infection of the Mexican bean beetle colony maintained at the Virology and Biocontrol Laboratory of the University of Arkansas. Partially purified extracts from ovarioles or entire beetles contained particles which, in negatively stained preparations, resembled reoviruses without the external protein coat. It is suggested that these particles represent a latent virus of the Mexican bean beetle.