Zethus (Zethastrum) Lopes, 2021

Lopes, Rogerio Botion, Carpenter, James M. & Noll, Fernando Barabosa, 2021, Cladistic analysis of Zethus Fabricius, 1804 (Hymenoptera, Vespidae): a new subgeneric classification, Journal of Hymenoptera Research 82, pp. 253-283 : 253

Zethus (Zethastrum) Lopes subg. nov.

Fig. 9

Type species.

Zethus ceylonicus de Saussure, 1867.

Description.

Male antennae hook-like. Interantennal carinas present or absent. Clypeus of female withour microstriae, short, usually with apical teeth. Male mandible with three or four teeth. Galea stub-like. Labial palpi 4-segmented with palpomere I straight (Fig. 9B ). Occipital carina ventrally complete. Vertex flat. Genal margin evenly convex. Pronotal carina short, slightly sinuous laterally. Pre-tegular carina absent. Welts absent. Notaulices complete. Tegula evenly convex with outer margin completely raised. Epicnemial carina variable. Mesepimeron without carina. Mid tibia with two spurs. Metanotum usually anteriorly margined, with lateral carina of variable length. Spines in posterior tibiae of females, when present, restricted to basal portion. Apical angle of marginal cell obtuse. Dorsal aperture of propodeum present. Submedian carina present (Fig. 9C ), but variable in the group; lateral carina present, with variable length; sublateral carina complete. Dorsal margin of propodeal orifice rounded or acute. Apical propodeal lamella triangular. T1 with short stem and long expansion with semi-parallel sides, with basal dorsal carina (Fig. 9C ). S1 with elliptical anterior margin. Lamella of T2 well developed. T3 with depression and lamella with confluent indent (Fig. 9D ). Lamella of T3 and S3 simple. S5 and 6 of males without carinas. Aedeagus with short basal plate. Digitus with basal projection and basal tuft.

Observations.

Only three of four species-groups from the Oriental region were sampled: Z. quadridentatus group (represented by Z. varipunctatus ); Z. luzonensis group (represented by Z. fulgens ); and Z. dolosus group (all the other Oriental Zethus ). Although the present analysis shows the basal longitudinal carina and weak apical constriction of T1 as synapomorphies for the subgenus and constant throut the clade, the sampling may not be as optimal as presumed, leaving out species with different traits than what was portrayed.

Wang et al. (2019) recently published three new species and a key to the Oriental species. The constriction of T1 is occasionally used in their key, highlighting the existence of specimens with a stronger constriction. However, this is not illustrated, making it impossible to determine to what degree the sclerite narrows. Still, clearly strong constrictions are illustrated for the newly described species Z. asperipunctatus Wang and Li and Z. nullimarginatus Wang and Li. The basal longitudinal carine of T1 was not used in the key, but in the two aforementioned species, the structure was not observed.

The Z. dolosus species group appears to be paraphyletic in relation to the Z. quadridentatus group. A thorough analysis is needed of Z. (Zethastrum) including representatives from the Zethus trimaculatus species group to verify the validity of the assemblages.

Although Gusenleitner (2007) described Z. fulgens comparing it to Z. nigerrimus , a species in the Zethus trimaculatus group, the type was examined, and it fits more properly the Z. luzonensis group. Selis (2017) recently revised this group, but left Z. fulgens out, just as Wang et al. (2019) did not key it in couplets along with the group. However, in its description (Gusenleitner, 2007), more emphasis is given to punctation and color and little attention is given to the pilosity, an outstanding and diagnostic trait of the group and so, it is no surprise Selis did not consider examining this species.

Distribution.

Palearctic and Oriental.

Included species-groups.

Zethus dolosus , Zethus luzonensis , Zethus quadridentatus , Zethus trimaculatus .

Etymology.

The subgeneric name comes from the radical Zethus accompanied by the suffix - astrum which stands for incomplete resemblance.

Included species.

29.

Figures

Figure 9. Synapomorphic characters of Zethus (Zethastrum) indicated in Z. ceylonicus A habitus B labial palpus C propodeum and basal portion of petiole, posterior view; arrowhead indicates submedian carina; arrow indicates basal longitudinal carina in first tergum D third metasomal tergum, lateral view; arrow indicates confluent indent. Scale bars: 1.0 mm.