Key to the males and females of Prodasineura species from Vietnam

Males of all Vietnamese species of Prodasineura can be separated into two main colourational groups (except for the sole black synthoracic species P. autumnalis) based on the colouration of the male thorax: the blue group (including P. coerulescens, P. hoffmanni and P. doisuthepensis) and the orange group (including P. croconota, P. verticalis, P. kong sp. nov. and P. lancastrei sp. nov.).

Males

1. Synthorax with whitish stripes, becoming very dark or complete black in fully mature individuals (Fig. 1A) ............................................................................................... P. autumnalis (Fraser, 1922)

– Synthorax with blue or yellow/orange stripes .................................................................................. 2

2. Synthorax and abdominal tip, sometimes including cerci with blue marking ................................. 3

– Thorax and head with red or orange pattern ..................................................................................... 5

3. Synthorax with large blue oval markings on mesepisternum (Fig. 2C) ............................................. ............................................................................................................. P. doisuthepensis Hoess, 2007

– Synthorax with a narrow antehumeral stripe .................................................................................... 4

4. S8–10 largerly blue, paraproct with blue marking (Fig. 3 A–B) ......... P. coerulescens (Fraser, 1932)

– S9 with a small blue dot, S10 largely blue, paraproct entirely black (Fig. 3 G–H) ............................ ............................................................................................................... P. hoffmanni Kosterin, 2015

5. Synthorax with large orange oval spots on mesepisternum ............................................................. 6

– Synthorax with narrow antehumeral stripe ...................................................................................... 7

6. The large oval marking never extending to the end of the mesepisterum (Fig. 6C); dorsal side of head mostly black with two small orange spots (Fig. 6A); appendages mostly yellow or blue (Fig. 7 A– B) .................................................................................................................... P. croconota Ris, 1916

– The large oval marking covering most of mesepisternum (Fig. 6D); wide transverse band on dorsal head side (Fig. 6E); appendages mostly black (Fig. 7 D–E) ......................... P. verticalis Selys, 1860

7. Wide transverse band on dorsal side of head (Fig. 9A); cerci posterior margin concave in lateral view; paraprocts yellowish apically (Fig. 9 C–D) ...................................................... P. kong sp. nov.

– Very narrow transverse band on dorsal side of head (Fig. 9B); cerci posterior margin concave in lateral view, axe-shaped; paraproct entirely black (Fig. 9 E–F).......................... P. lancastrei sp. nov.

Females

We collected all studied species of Prodasineura in Vietnam in pair or tandem in order to exactly define the female of each species, except for the female of P. hoffmanni, which is still lacking in our collection. All characters of the female of P. hoffmanni used in this key are adopted from Kosterin (2015).

1. Posterior pronotal lobe with three flattened projections without a pair of ear-like structures (Fig 13 E– F) ....................................................................................................................... P. lancastrei sp. nov.

– Posterior pronotal lobe with two horns and two adjacent ear-like structures ................................... 2

2. Posterior pronotal lobe possesses two long sharp horns, strongly upward curving (Fig. 13 G– H) .................................................................................................................. P. verticalis Selys, 1860

– Posterior pronotal lobe with two short and robust horns .................................................................. 3

3. The horns well developed, smoothly curving anteriorly in lateral view .......................................... 4

– The horns very short, slightly raising anteriorly in lateral view (Fig. 5 A–B) .................................... ............................................................................................................... P. autumnalis (Fraser, 1922)

4 The pair of raised processes small, well separated (Fig. 5 D–E) ........ P. coerulescens (Fraser, 1932)

– The pair of raised processes well developed, positioned more centrally ......................................... 5

5 The robust horns curving upward, two ear-like structures well separated by a space greater than their own diameter (Fig. 13 C–D) ....................................................................................... P. kong sp. nov.

– The robust horns strongly curving anteriorly, two ear-like structure are set closer to each other, separated by a broad incision (Fig. 5C) ............................................................................................ 6

6 Dorsal side of head and thorax with yellowish pattern (Fig. 6B) ................... P. croconota Ris, 1916

– Dorsal side of head and thorax with blue pattern (Fig. 2E, G) ......................................................... 7

7 Anteclypeus black, two ear-like structures are set closer to each other and converging, separated by a roundish incision (Kosterin 2015) (Fig. 5F) ...................................... P. hoffmanni Kosterin, 2015

– Anteclypeus ochre-yellow with a black central stripe (Fig. 2E), two ear-like structures separated by a broad semicircular incision, not converging (Kosterin 2015) (Fig. 5C) .......................................... ............................................................................................................. P. doisuthepensis Hoess, 2007