About Macrosiagon limbatum (Fabricius, 1792)
Macrosiagon limbatum (Fabricius, 1792), also referred to as Macrosiagon limbata, is a species of wedge-shaped beetle in the family Ripiphoridae. It is found across the Eastern United States, Southeastern Canada, and Central America. Its range may extend into South America, though this has not been confirmed. Beetles in the genus Macrosiagon are internal parasites of other insects during one stage of their lifecycle, and undergo hypermetamorphosis, meaning their larvae pass through multiple morphologically distinct instar stages.
Females of this species lay eggs on flowers that are visited by bees and other hymenopterans. Larvae of Macrosiagon limbata have been documented as parasites of the wasp family Crabronidae. The first larval instar is a planidum, an active larva that can climb onto a host hymenopteran. After that, the larva is carried to the host's nest, where it acts as a parasitoid. Subsequent instars do not have legs, and feed on the host's larvae or the nest's stored pollen and nectar supplies.
Adult Macrosiagon limbata are active in the summer, and can be found on flowers including elderberries and goldenrod. They have elongated mouthparts that are thought to be used for sucking nectar. Males have comblike antennae, while female antennae are serrate. The elytra of this species are longer than the abdomen, and diverge at the apex.
