I compared the density and infestation rate of melon fly (Dacus cucurbitaeCoquillett) in papaya (Carica papayaL.) fruits on the ground and on trees and correlated the density and level of melon fly infestation in fruits with the relative density of adults in papaya orchards. Melon fly larval density was significantly higher in papaya fruits on the ground than on trees. The relative density of melon fly adults in the orchard correlated significantly with larval density in fallen fruits, but not with larval density in tree fruits. In addition, the number of adults in the orchard had a higher significant correlation with the melon fly percentage infestation in fruits on the ground than with the melon fly percentage infestation in tree fruits. Results suggest that papaya fruits left on the ground serve as a major breeding site and, thus, as a reservoir of resident (non-immigrant) melon fly population in papaya growing areas of Hawaii. Sanitation (removal of fallen fruits) should be an integral component of control methods aimed at managing melon fly population in papaya orchards.