Predator palatability in two Neotropical species of Sepsidae (Diptera, Sciomyzoidea)

Abstract

Chemical defense consists of the usage of substances that can cause damage to the predator or repel their attacks. A few true fly (Diptera) species use chemical defenses and among the adult ones, these mechanisms have only been formally registered in the family Sepsidae. Some species of this family possess an abdominal gland (Dufour gland) that produces a substance with a characteristic and intense odor. This odor supposedly turns the sepsids unpalatable to their predators. However, there is no study testing this hypothesis with Neotropical species yet. Thus, the aim of this study is to verify if two neotropical species of Sepsidae (Archisepsis armata and Microsepsis armillata) are unpalatable to invertebrate predators (jumping spiders, giant crab spiders, and mantises). The experiment consisted in offering specimens of sepsids (treatment group) and fruit flies (drosophilids; control group) to three species of predators. Furthermore, a study of the internal morphology of the two sepsid species has been performed to verify the presence of the Dufour gland. There has not been any significant predation difference between the sepsids and the control group, and the Dufour gland has not been found in both of them. This data suggests that both neotropical species of sepsids are not unpalatable.