Key to species of the Deltocephalus from China (Males)

1. Style apophysis more than 0.33 total length of style (Figs 1 A, 2E); apical margin of aedeagus entire (Figs 1D, 2D)........ 2

- Style apophysis less than 0.33 total length of style (Figs 3D, 4 E); apical margin of aedeagus notched (Figs 3 E, 3G, 4G)..... 3

2. Aedeagal shaft with subapical ventral margin serrate (Fig. 1 E)......................................... D. pulicaris

- Aedeagal shaft with subapical ventral margin smooth (Fig. 2 B)...................................... D. nigriventris

3. Subgenital plate subtriangular (Fig. 3 C); apex of aedeagal shaft directed dorsad, apical notch shallow (Figs 3 E–H)..................................................................................................... D. vulgaris

- Subgenital plate wide triangle (Fig. 4 C); apex of aedeagal shaft directed cephalad, apical notch deep (Figs 4 G, 4H)............................................................................................. D. uncinatus sp. nov.