An iridescent virus is found at low prevalence in population of Aedes taenirhynchus. Attempts at experimental transmission produced low levels of infection, regardless of the dosage applied. In a test for genetic resistance in colonized Ae. taeniorhynchus, the mean infection rates +/- SD for groups of randomly selected and sibling larvae were compared. The standard deviation of the sibling groups was not higher than the random groups (4.0 +/- 3.1% and 3.0 +/- 2.1%), rendering genetic resistance unlikely. Injury to the larvae by feeding silicon carbide fibers consistently caused higher infection rates (4.8 +/- 2.0% by virus alone and 17.5 +/- 5.3% by virus and fibers concurrently). Similar results were obtained for vertical transmission. These results support the hypothesis that this virus has no active means of penetration, invading only through random breaks in the cuticle or peritrophic membrane.