Key to species (males) of Longicornus (Modified from Fang & Xing, 2019)

1. Aedeagal shaft with pair of processes arising basally (Figs. 19,20,25,26)..........................................

- Aedeagal shaft with a pair of processes arising apically(Figs. 21,22,23,24,27,28,32,33)...............................

2. Aedeagal shaft with pair of furcate processes arising from ventral margin near base (Figs. 25,26)............... L. furcatus

- Aedeagal shaft with two pairs of processes medially on dorsal margin (Figs.19,20)....................... L. biprocessus

3. Aedeagal shaft processes about as long as shaft (Figs. 23,24,32,33).............................................. 4

- Aedeagal shaft processes shorter than shaft (Figs. 21,22, 27,28)..................................................

4. Aedeagus with furcate process arising apically in lateral view(Figs.32,33)........................... L. grossus sp.nov.

- Aedeagus with slender process arising apically in lateral view(Figs.23,24)............................ L. flavipuncatus

5. Aedeagus long, with apical processes shorter than ⅔ length of shaft (Figs.27,28)............................. L. longus

- Aedeagus short and stout, with apical processes shorter than ¼ length of shaft (Figs.21,22)................. L. brevispinus