Platylabus Wesmael, 1845

Platylabus Wesmael, 1845: 150 .

Type species: Platylabus rufus Wesmael, 1845, by subsequent designation of Ashmead (1900a: 19).

Comparative diagnosis

The genus can generally be easily distinguished from Cyclolabus by the structure of the propodeal spiracles which are longer than wide (Figure 19b). However, as already discussed (see Cyclolabus), some small species of Platylabus approach a rather circular shape for the propodeal spiracles and can be difficult to tell apart from Cyclolabus species. In addition to the propodeal spiracle, Platylabus can be easily distinguished from all the other genera by the following characters: the apices of areae dentiparae are always without long apophyses (at the most with tooth-like projections, as in Figure 22b); the area superomedia is clearly defined (Figure 5a) and not merging with area basalis as in Ambloplisus (Figures 5c–5d); the gastrocoeli are transverse, deeply impressed, and usually considerably wider than the interval between them (Figures 19a, 20a, 20e, 22a); the apex of the metasoma is always without white anal spots (Figures 22a, 22d, 26a, 26d); the mandibles are not twisted (Heinrich 1977; Tereshkin 2009). For a full account of the differences between Platylabus and Tropicolabus, see under the latter genus.

Range and diversity

Platylabus has a worldwide distribution and with its 40 species in the Nearctic, it is the largest genus among Nearctic Platylabini . In the south-eastern United States, six species have been recorded so far (Heinrich 1977; Yu et al. 2016).

Key to the species of Platylabus from the south-eastern United States (adapted from Heinrich (1962b) and Heinrich (1975))

Males of P. flavidoclarus Heinrich, 1977 and P. rubristernatus Heinrich, 1962 are unknown.

1. Female...................................................................................................................................... 2

- Male.......................................................................................................................................................... 8

2. Metasoma bright metallic blue (Figure 22d) ........................................................................... 3

- Metasoma of different colour (Figures 26d, 28c, 30c, 32b, 32d) ..................................... 5

3. Postepetiole and hind femur with apical yellow bands; malar space yellow; sculpture of tergites fine .............................................................................. flavidoclarus Heinrich, 1977

- Postpetiole and hind femur without apical yellow bands (Figure 22b); malar space not yellow marked (Figure 22c); sculpture of tergites coarse........................................... 4

4. Flagellum distinctly to considerably widened beyond the middle (Figures 22a, 22b) .......................................................................................................................... clarus (Cresson, 1867)

- Flagellum not at all widened beyond the middle.................. hyperetis Heinrich, 1962

5. Metasoma ferruginous, with yellow posterior bands on tergites 1–3 (Figure 28c)....... ................................................................................................................ ornatus (Provancher, 1875)

- Metasoma black (Figure 26d).......................................................................................................... 6

6. Coxae entirely black (Figure 26b)........................ opaculus americanus Heinrich, 1962

- Coxae entirely ferruginous or sometimes with white spots, never with black markings (Figures 30c, 32b)............................................................................................................. 7

7. Scutellum entirely white, convex, laterally not carinated except anteriorly (Figure 32a); gastrocoeli less marked and not as distinctly wider than the interval between them as in the following species; reddish-orange colouration on the mesopleuron, metapleuron and mesosternum more extensive (Figure 32b).............................................. .......................................................................................................... rubristernatus Heinrich, 1962

- Scutellum apically white and anteriorly black, carinate beyond the middle (Figure 30a); gastrocoeli strongly marked, distinctly wider than the interval between them (Figure 30a); reddish-orange colouration on the mesopleuron reduced to a spot in the postero-ventral corner (Figure 30c)............................................... ................................................................................................... rubricapensis (Provancher, 1882)

8. Metasoma bright metallic blue (Figure 22d)............................................................................ 9

- Metasoma of different colour (Figures 26d, 28c, 30c, 32b, 32d)................................... 10

9. Outer orbits white from temple region down to base of mandibles, white colour gradually widening downward over most of the surface of apical part of cheeks; flagellum without annulus.................................................................... clarus (Cresson, 1867)

- Face and clypeus entirely white; flagellum with annulus.... hyperetis Heinrich, 1962

10. Metasoma ferruginous-red, with a yellow posterior band on tergites 1–3...................... ................................................................................................................ ornatus (Provancher, 1875)

- Metasoma black................................................................................................................................. 11

11. Coxa III entirely or predominantly black; face black with inner orbit white .................... ........................................................................................... opaculus americanus Heinrich, 1962

- Coxa III entirely or predominantly red or ferruginous; face either entirely white or black with inner orbits white .......................................................... rubricapensis Provancher, 1882