Biology and morphology of the jelly fungus-feeding sawfly Decameria interrupta (Fabricius, 1804) (Hymenoptera: Pergidae: Perreyiinae)

Abstract

The larvae of the Neotropical sawfly Decameria interrupta (Pergidae: Perreyiinae) are documented here for the first time. They feed on the jelly fungus Auricularia fuscosuccinea in the Brazilian Atlantic Forest. Morphological characterisation reveals unique elongated tubercles on the thorax and abdomen and substrate-mimicking colouration in the full-grown larvae, while the prepupae undergo significant colour changes (grey/orange to light pink) and construct thick black cocoons. We established new state records for São Paulo and redescribed the adult female with its ovipositor. The rare mycophagous habit, only the second record in all Tenthredinoidea and both within Perreyiinae, is associated with the vestigial ovipositor of this sawfly species, consistent with the small ovipositor of females in the Perreyia genus group and their unusual larval diet. Taxonomic discrepancies regarding prior host records are addressed, underscoring the need for integrative studies on sawfly trophic ecology.