Posterior region of adult fly (ex McAlpine 1981).
As in all insects, the abdomen of a fly is primitively composed of 11 segments. The terminal portion, consisting of the rudiments of segment 11, namely a pair of cerci and the anus, is called the proctiger. There is no evidence of a 12th segment.
The basal segments of the abdomen (preabdomen), consisting of segments 1-5 or 1-6, are frequently broader than the terminal portion of the abdomen, referred to as the terminalia (postabdomen, hypopygium). Basically each abdominal segment consists of a dorsal tergite and a ventral sternite connected laterally by the pleural membrane. Of special interest are one or more pairs of sensory setulae (alphasetae, sensilla trichodia) that are frequently present on the anterior margin of the sternites (ex McAlpine 1981).
adj.: abdominal