Description of a prosternal sensory organ in a wood gnat (Diptera: Anisopodidae)

A prosternal sensory organ in muscoid flies consists of paired fields of mech-anoreceptive hairs located on the presternum. These hairs provide proprioceptive information about the posture of the fly's head relative to the thorax. Scanning electron microscopy of the prosternal region of the wood gnat Sylvicola punctatus (Fab.) (Diptera: Anisopodidae) has revealed an unpaired midline structure that shares many of the morphological characteristics of the paired prosternal organ found in the Brachycera. Thus, this unpaired prosternal organ of Sylvicola likely represents a homologous structure found for the first time in the Nematocera.