This passage initially referred solely to viruses that had been confirmed to be passed through the salivary glands of leafhoppers (as reported by L. M. Black in The Viruses, Volume 2: 157-185, a 1959 publication edited by F. M. Burnet and W. M. Stanley, and released by Academic Press in New York and London). These types of viruses can be discovered in the insect’s hemolymph and endure for an extended duration within the insect and throughout its molting process.