Scientific name: Prodasineura autumnalis

Habitat: slow-flowing stream

Body length: 38-40 mm

Distribution in Hong Kong: widespread, e.g Wu Kau Tang, Hok Tau, Mui Wo

Flight period in Hong Kong: April to November

Similar species: Orange-backed Threadtail (Comparison: female)

Identification features (male):

1. Synthorax and abdomen black

Identification features (female):：

1. Synthorax black

2. Two white or pale orange stripes at two sides of synthorax respectively

3. End of yellow spots at two sides of the 2nd abdominal segment hook-like