DESCRIPTION OF A PROSTERNAL SENSORY ORGAN IN A WOOD GNAT (DIPTERA, ANISOPODIDAE)

A prosternal sensory organ in muscoid flies consists of paired fields of mechanoreceptive hairs located on the presternum. These hairs provi de proprioceptive infermation about the posture of the fly's head rela tive to the thorax. Scanning electron microscopy of the prosternal reg ion of the wood gnat Sylvicola punctatus (Fab.) (Diptera: Anisopodidae ) has revealed an unpaired midline structure that shares many of the m orphological characteristics of the paired prosternal organ found in t he Brachycera. Thus, this unpaired prosternal organ of Sylvicola likel y represents a homologous structure found for the first time in the Ne matocera.