Lissocephala powelli (Diptera: Drosophilidae)—high resolution diagnostic images

The Christmas Island Crab Fly—Lissocephala powelli Carson & Wheeler, 1973—is found only on Christmas Island (Australia, NE Indian Ocean) where it breeds on the land crabs Gecarcoidea humei and Birgus latro. Lissocephala powelli is listed as Australian, but biogeographically it is Oriental—Christmas Island is about 350 km from Java and 1,520 km from mainland Australia. The species is common on the island and easily collected directly from crabs as they move around in forested areas. In the description, Carson & Wheeler (1973, Pacific Insects 15: 199–208) highlighted the difference in pleural coloration between it and the widespread species L. metallescens (de Meijere, 1914) (type locality: Java)—L. powelli has a darkened upper pleural stripe (Fig. 4), compared to other species of Lissocephala e.g., L. metallescens, L. fijiensis Harrison, 1954 and L. versicolor Malloch, 1934, all lacking a stripe (imaged by McEvey, 2026a,b,c,d). A minute proepisternal seta is present in this species (Figs 6, 7) and in L. versicolor but not in L. metallescens or L. fijiensis; this has not previously been reported. Note also the darkened tarsomere 5 (Fig. 5), not present in the other species mentioned. A second undetermined Lissocephala species (database name: Lissocephala sp21890. McEvey) was collected on Christmas Island in 2003 by the author and in 2019 by Anthony Postle. The species is much darker than L. powelli—the thorax and abdomen are entirely black, the foreleg is pale and the mid and hind legs are darkened: femora darkened in distal half, tibiae entirely blackish, tarsi, including tsm 5, pale (specimens in AM).