Resumo. The members of the family Phoridae (Insecta: Diptera), whose adults are commonly known as scuttle fly or humpbacked fly, differ widely as to their feeding habits in the larval and adult stages. Dipteran larvae of Megaselia Róndani, 1856 (Diptera: Phoridae) vary considerably in feeding habits. The results of this study confirm the parasitic and frugivorous habits of Megaselia larvae. Megaselia scalaris (Loew, 1866) behaved as primary parasitoid of Isognathus caricae (L., 1758) (Lepidoptera: Sphingidae) larvae in confinement using cage under laboratory conditions. It is also the first time the frugivorous habit of M. scalaris larvae is recorded in ripe fruits of the avocado tree (Persea americana, Lauraceae) under field conditions.