This study addressed the potential effects on Hawaii's unique fauna of protein bait sprays used in fruit fly eradication programs. We sampled the ground litter-inhabiting invertebrates attracted to protein hydrolysate-baited pitfall traps at six localities on the island of Kauai. Twenty-two taxa and possibly 30 species were found in significantly higher numbers in treatment than in control traps. A diverse fauna, including species of land snails (Gastropoda), isopods (Isopoda), millipedes (Diplopoda) and insects (nine families), was attracted to the bait. Flies in the family Drosophilidae may be particularly susceptible to bait sprays, with at least eight species demonstrating attraction. Traps in high-elevation native forest attracted the highest number of species (20) and the most native species (11). The number of native species attracted to the bait decreased with elevation and the proportion of native vegetation, so that no native species were recovered from the two low-elevation agricultural areas. The potential effect of using protein hydrolysate bait sprays for alien fruit fly control in Hawaii is discussed.