About Didea alneti (Fallén, 1817)
This species is Didea alneti (Fallén, 1817). For morphological terminology, refer to the Morphology of Diptera. This species has a wing length of 9.75-11.5 mm. Its face is mostly yellow. The knob of the haltere is at minimum black or dark brown. The male vertex is not long, and it is less narrow than the vertex of Didea fasciata. The fifth abdominal tergite is black, and rarely bears spots. In male fourth tergites, the front edge of the wedge-shaped bars is clearly separated from the front margin of the tergite, or just touches the front of the tergite along the median line. Both the male genitalia and the larva of this species are illustrated in Dusek and Laska (1967). Didea alneti is a Palearctic species. It has a wide distribution across Europe, and extends east through Russia to the Pacific coast, as well as occurring in Mongolia, Japan, and Korea. In North America, it ranges from Alaska south to Colorado.
