Zethus, Fabricius, 1804, Fabricius, 1804

Lien Thi Phuong Nguyen & James M. Carpenter, 2016, Taxonomic review of the genus Zethus Fabricius (Hymenoptera: Vespidae: Eumeninae) from Vietnam with descriptions of four new species, Entomological Science 2016, pp. 1-9 : 8

KEY TO SPECIES FROM VIETNAM

The characters used are applicable to both sexes unless the sex is specified. The characteristics of Z. nigerrimus are taken from Gusenleitner (2010).

1 Propodeum shiny, with lateral carinae. Metasomal segment I with tergum and sternum fused, leaving suture between them distinct throughout the segment … ........................................................................2

- Propodeum dull, without lateral carinae. Metasomal segment I with tergum and sternum fused, without suture between them, only small and well defined punctures present … ................................................ 7

2 Metasomal segment I long and thin, 3.5× as long as wide. SII in lateral view tuberculate two-fifths distance from base … ................... Z. dolosus Bingham

- Metasomal segment I shorter and thicker, equal or less than 3× as long as wide. SII in lateral view not tuberculate … ..........................................................3

3 Head and thorax with long hairs, 2× as long as ocelli diameter … ...................... Z. nigerrimus Gusenleitner

- Head and thorax with shorter hairs. … ........................4

4 Male: Area around ocelli not swollen. Apical margin of clypeus slightly emarginated. FXI small, not curved, bullet shaped, as wide as long. Submarginal carina produced into rounded lamella above propodeal valvulae. Metasomal segment I strongly swollen … .............................. Z. trimaculatus Cameron

- Male: Area around ocelli swollen. Apical margin of clypeus strongly emarginated medially with the emargination nearly half circle. FXI slightly curve, longer than wide. Submarginal carina produced into pointed lamella above propodeal valvulae. Metasomal segment I less swollen … ...........................5

5 Male: Metasomal segment I longer, 3× as long as wide. TII in lateral view strongly concave near base. SII in lateral view angular at basal half with obtuse angle. … .................................................. Z. angulatus sp. nov.

-Male: Metasomal segment I shorter, less than 2.5× as long as wide. TII in lateral view slightly concave near base. SII in lateral view gradually convex from base to apical margin … .......................................................6

6 Male: Ocelli small, about half antennal socket diameter. FXI long and thin, 2.8× as long as it basal width. … ....................................... Z. tansoneus sp. nov.

- Male: Ocelli large, about as wide as antennal socket diameter. FXI thick, 2.3× as long as it basal width. … .................................................... Z. tumidus sp. nov.

7 Head and thorax covered with dense and long hairs, 2× as long as ocellar diameter. Submarginal carina produced into short and round lamella above propodela valvulae … ..................................... Z. propodeus sp. nov.

- Head and thorax covered with shorter hairs. Submarginal carina produced into long and pointed lamella above propodeal valvulae … ............... Z. malayanus Gusenleitner