Genus Limnocoris Stål, 1860

Limnocoris Stål, 1860: 83. Type species: Limnocoris insignis Stål, 1860, by monotypy.

Discussion. In the present study, the synonymies of three species, the descriptions of five new species, and the elevation of a subspecies to full species status are proposed. These taxonomic actions bring the total to 12 species of Limnocoris for the Guiana Shield and Amazon regions (Table 1), and a total of 75 valid species for the genus.

Key to the species of Limnocoris of the Guiana Shield and Amazon regions

Three species treated by Rodrigues & Sites (2021) also occur in the area considered in the present study and are included in the key: L. illiesi De Carlo, L. pusillus Montandon, and L. reynosoi Rodrigues & Sites; these species were diagnosed and illustrated in the corresponding study. We also include Limnocoris minutus De Carlo, a species recorded in Paraguay and Brazil (Mato Grosso and Mato Grosso do Sul) (De Carlo 1951; Pagioro et al. 2007; Floriano et al. 2013), which might also occur in the area considered here.

1. Mesosternum without longitudinal row of elongate golden setae (Fig. 1A) (some specimens may have golden setae on mesosternum, but not forming a distinct row); sternum II with patch of elongate golden setae (Fig. 1I) or without elongate golden setae (Fig. 1J).................................................................................. 2

- Mesosternum with longitudinal row of elongate golden setae (Fig. 1B); sternum II with sinuous row of elongate golden setae (Fig. 2B)............................................................................................ 6

2. Propleuron almost completely shagreened, with just narrow pruinose band posteriorly (Fig. 9C); propleuron posterior margin shallowly convex at mid-length (Fig. 9C); hemelytra reduced after embolium, exposing wide area of abdominal terga III–VI (Fig. 9A)....................................................................... Limnocoris moreirai n. sp.

- Propleuron with shagreened area extending posteriorly along lateral margin (Fig. 1C); propleuron posterior margin almost straight or shallowly concave at mid-length (Fig. 1A); hemelytra not reduced after embolium, exposing just a narrow area of abdominal terga III–V................................................................................. 3

3. Mesosternal carina transversely notched (Fig. 11E)................................... Limnocoris yanomami n. sp.

- Mesosternal carina with lateral margins intact, not notched (Figs. 1D–F)...........................................4

4. Abdominal sternum II with patch of elongate golden setae (Fig. 1I); female subgenital plate narrowly rounded or subtriangular posteriorly (Fig. 1M)....................................................... .. Limnocoris pusillus Montandon

- Abdominal sternum II without patch of elongate golden setae (Fig. 1J); female subgenital plate with posterior margin broadly rounded (Fig. 1K) or almost truncate (Fig. 1N)...............................................................5

5. Mesosternal carina with median ridge terminating in short setae-covered tooth close to anterior margin of fossa (Fig. 1E); posterolateral corner of abdominal tergum III produced, spinose (Fig. 1H); female subgenital plate with posterior margin almost truncate (Fig. 1N).................................................... .. Limnocoris reynosoi Rodrigues & Sites

- Mesosternal carina with median ridge without setae, and terminating midway between anterior projection and fossa or near base of fossa (Fig. 1F); posterolateral corner of abdominal tergum III right angled, sometimes acute but not produced; female subgenital plate with posterior margin broadly rounded (Fig. 1K)......................... Limnocoris illiesi De Carlo

6. Mesosternal carina narrow, with fossa ca. 2× width of median ridge; metasternal carina with a sharp midline ridge, without evident fossa (Figs. 5C, E); ventral color of body yellow, with dark-brown along posterior margin of propleura to middle of metapleura (Fig. 5B)............................................................. Limnocoris flavescens n. sp.

- Mesosternal carina broad, with fossa>2× width of median ridge; metasternal carina broad, fossa well-developed and oval to teardrop-shaped (e.g., Figs. 2B, 3D, 4D); ventral color of body light-brown to brown, without dark-brown area along posterior margin of propleura to middle of metapleura (e.g., Fig. 2B).................................................... 7

7. Shagreened area of propleuron not extending posteriorly along lateral margin (Fig. 2B)...... Limnocoris amazonensis n. sp.

- Shagreened area of propleuron extending posteriorly at least halfway along lateral margin (Figs. 3D, 7C, 8D, 10C)........ 8

8. Abdominal sterna III–V with rounded dark-brown spots near lateral margins (Figs. 4E, 8F, 10B); serration of abdominal tergum V with 11–19 teeth, usually fewer than 19 (Figs. 4E, 8F, 10D).................................................. 9

- Abdominal sterna III–V without rounded dark-brown spots near lateral margins (Figs. 3B, 7B); serration of abdominal tergum V with 19–23 teeth (Figs. 3E, 7E)....................................................................... 12

9. Posterolateral corners of abdominal terga III–V yellowish; serration of abdominal tergum V with 17–19 teeth (Fig. 4E); posterior margin of male abdominal tergum VII distinctly projected medially, truncate (Fig. 6E)....... Limnocoris fittkaui De Carlo

- Posterolateral corners of abdominal terga III–V dark-brown, or III–IV yellowish and V dark-brown; serration of abdominal tergum V with 11–16 teeth (Figs. 8E, 10D); posterior margin of male abdominal tergum VII not distinctly projected medially, convex (as in Fig. 12C)............................................................................... 10

10. Posterolateral corner of abdominal tergum IV usually dark-brown (Fig. 8E); female subgenital plate with lateral margin straight or slightly convex in anterior half, posterior margin broadly rounded (Fig. 8F)............. Limnocoris menkei La Rivers

- Posterolateral corner of abdominal tergum IV yellowish; female subgenital plate with lateral margin slightly concave in anterior half, posterior margin rounded, narrower (sometimes just slightly) medially (Figs. 1L, 10E)......................... 11

11. Body length 6.40–6.80; serration of abdominal tergum V with 11–13 teeth................ Limnocoris minutus De Carlo

- Body length 7.35–8.10; serration of abdominal tergum V with 13–16 teeth (Fig. 10D)................................................................................................... Limnocoris surinamensis Nieser n. stat.

12. Embolium with lateral margin shallowly convex, widening to broadly rounded inflection in posterior third, and margin almost straight to shallowly concave posteriorly (Figs. 3A–C)............................. Limnocoris burmeisteri De Carlo

- Embolium with lateral margin mostly straight in anterior 2/3, dramatically widened in posterior third, inflection narrowly rounded and margin distinctly concave posteriorly (Fig.7A)............................... Limnocoris inflatus n. sp.