Xenogenus gracilis ( Reed, 1899 )

Diez, Fernando & Coscarón, María Del Carmen, 2015, Contribution to the knowledge of Patagonia, Argentina: redescription of the genus Xenogenus Berg 1883 (Hemiptera: Heteroptera: Rhopalidae) and description of immature stages of Xenogenus gracilis Reed, 1899, Zootaxa 3919 (3), pp. 573-582 : 574-579

Xenogenus gracilis ( Reed, 1899)

( Figs. 1 A–B, 1D–E) ( Figs. 2 A–E) ( Figs. 3 A–D)

1899 Harmostes gracilis Reed , 3: 44.

1942 Xenogenus gracilis: Harris , 16: 360

Distribution in Argentina. Buenos Aires: Felipe Solá, La Plata; Catamarca: Miraflores; Córdoba: La Puerta; La Pampa: Gral. Pico, La Rioja: Nonogasta; Quimilí; Tucumán: La Cocha, Trancas ( Pall et al. 2013).

Distribution outside Argentina. Chile: Bañados de Cauquenes ( Reed 1899; Göllner-Scheiding 1983).

Material examined. Argentina: Chubut: Los Altares (5♂, 5♀) Diez- Coscarón- Pall- Quirán col. 21/II/2013; altitude 253 meters, time: 20:00 hr.

New record. Argentina: Chubut: Los Altares.

Observation. The host plant preferences of the Chorosomatini have typically been reported to be grasses ( Schaefer & Chopra 1982; Schaefer & Mitchell 1983). But we collected nymphs and copulating adults on the same plant, Salsola sp. ( Chenopodiaceae ). Being the first record of Rhopalidae on Chenopodiaceae host plant.

Remarks. Due to that great similarity between these two species, there were, unfortunately, misidentifications in Pall et al. (2013). The distributions we cite in the paper from Pall et al. (2013) have been corroborated with material from MLP.

Overall color light brown; in females, the overall color of some specimens is from light brown to light yellow. Postocular region, pronotum, propleuron, mesepisternum, mesepimeron, osteolar peritreme, scutellum, femora, tibiae, corium and ventral surface of abdomen with red to dark brown dots ( Fig. 1 A–B). Body covered with abundant whitish pilosity. Head 1.20–1.50 times longer than head width. Head 1.77 (1.97 in female) times longer than anteocular region length. Head in dorsal view with two longitudinal dark brown bands, from ocelli to anterior margins of eyes and one irregular spot in the middle ( Fig. 1 A–B). Lateral view with one dark brown line from posterior margins of the head to anterior margins of antenniferous tubercles. Labium reaching the posterior margin of the metasternum; first segment not surpassing the posterior margin of the eye. Ratio of labial segment lengths: 1: 1.09: 0.74: 0.72. Ratio of antennal segments: 1: 3.31: 3.62: 3.50. First antennal segment length 0.33–0.43 times as short as head length. Lateral and ventral surface of first antennal segment dark brown. Second and third antennal segments with a thin reddish line in dorsal and ventral sides. In some specimens with second antennal segment and third antennal segment totally light brown. Pronotum 1.46– 1.74 times wider than pronotum length. Anterior and posterior lobes clearly separated, anterior lobe with two depressions, posterior lobe coarsely punctate, posterior margin softly convex. Median longitudinal keel conspicuous, more conspicuous on the anterior lobe. In some specimens pronotum partially to totally dark brown ( Fig. 1 A–B). Whitish setae on lateral margins of the scutellum and posterior process rounded. Posterior femora longer than fore and middle femora, 1.76–1.93 times as long as fore femora, and 1.68–1.97 times as long as middle femora. Hind tibiae very long, 2.19–1.01 times longer than fore tibiae and 1.09–1.65 times longer than middle tibiae. First tarsi and hind tibiae black distally, third tarsi black. Hemelytra: corium and clavus hyaline, red dots on veins of corium; membrane hyaline, in some specimens with red dots and surpassing apex of abdomen. Abdomen, with red spots on ventral surface, more densely towards lateral margins.

Male genitalia. ( Figs. 2 A–E). Pygophore with lateral lobes triangular ( Fig. 2 A–C); paralateral lobes triangular and apex round ( Fig. 2 B); paramere curved, large and protruding (the apex of the lateral lobes reach the middle of the paramere) ( Fig. 2 A–B). Internal margin of paramere curved inwards, distally contracted, apex triangular and acuminate ( Fig. 2 E).

Immature stages ( Figs. 3 A–D)

Instar II: ( Fig. 3 A) (n=5) General color similar to instar V. Total length 2.50–2.90 (mean = 2.74). Head: length 0.64–0.81 (mean = 0.76), width 0.56–0.60 (mean = 0.57); width of eyes 0.09–0.12 (mean = 0.11), interocular width 0.38–0.48 (mean = 0.43). Labium passing beyond metacoxae, Ratio of labial segment lengths 1: 0.75: 0.77: 0.98. Antennae setose, abundant distally, ratio of segment lengths 1: 2.66: 2.70: 3.04. Pronotum length 0.24–0.30 (mean = 0.27), width 0.70–0.75 (mean = 0.72). Wing pad length 0.32–0.35 (mean = 0.34). Abdomen: length 1.61–1.74 (mean = 1.66), width 1.08–1.25 (mean = 1.17). Abdomen with four dark tubercles with one seta in the apex and five to eight small, hyaline tubercles scattered on the dorsal surface of abdomen.

Instar III: ( Fig. 3 B) (n=5) General color similar to instar V. Total length 3.49–3.63 (mean = 3.52). Head: length 0.84–1.00 (mean = 0.91), width 0.64–0.70 (mean = 0.67); eyes width 0.12–0.16 (mean = 0.14), interocular width 0.46–0.52 (mean = 0.48). Ratio of labial segment lengths about 1: 0.85: 0.50: 0.83. Antennae setose, abundant distally, ratio of segment lengths 1: 2.54: 2.61: 3.25. Pronotum length 0.28–0.36 (mean = 0.32), width 0.83–0.97 (mean = 0.90). Wing pad length 0.64–0.68 (mean = 0.65). Abdomen: length 1.81–2.24 (mean = 2.03), width 1.32–1.48 (mean = 1.39). Abdomen with six dark tubercles with one seta in the apex and three to six small, hyaline tubercles scattered on the dorsal surface of abdomen.

Characters Xenogenus gracilis Xenogenus picturatum

N= 5 Male N= 5 Female N= 4 Male

Instar IV ( Fig. 3 C) (n=5) General color similar to instar V. Total length 3.82–4.22 (mean = 4.06). Head: length 0.80–0.89 (mean = 0.84), width 0.70–0.76 (mean = 0.72), eyes width 0.14–0.16 (mean = 0.15), interocular width 0.52–0.56 (mean = 0.54). Ratio of labial segment lengths about 1: 1: 0.62: 0.83. Ratio of antennal segment lengths 1: 2.67: 2.70: 3.16. Pronotum light brown with red dots, length 0.30–0.38 (mean = 0.34), width 0.88–0.94 (mean = 0.91). Wing pad light brown, length 0.80–0.83 (mean = 0.81). Abdomen: length 2.07–2.40 (mean = 2.24), width 1.18–1.65 (mean = 1.42). Abdomen with ten dark tubercles with one seta in the apex and numerous small, hyaline tubercles scattered on the dorsal surface of abdomen.

Instar V: ( Fig. 3 D) (n=5) Overall color light brown, ventral surface pale yellowish. Dorsal surface with sparse long black setae ( Fig. 3 D). Total length 5.9–6.4 (mean = 6.16) Head: length 0.99–1.18 (mean = 1.10), width 0.72–0.89 (mean = 0.80), dorsal view with reddish dots and one longitudinal red line in lateral view, from eyes to antenniferous tubercles ( Fig. 3 D); eyes width 0.19–0.26 (mean = 0.22), interocular width 0.56–0.62 (mean = 0.59). Rostrum passing beyond metacoxae, ratio of segment lengths about 1: 0.86: 0.63: 0.75. Antennae light brown, first antennal segment dark brown, second and third antennal segments with one longitudinal, reddish line in dorsal and ventral surface ( Fig. 3 D), setose, abundant distally, ratio of segment lengths 1: 2.57: 2.54: 3.26. Pronotum light brown with red dots, posterior edges brown; length 0.45–0.50 (mean = 0.46), width 1–1.35 (mean = 1.22). Wing pad light brown with the internal edges brown to dark brown and red dots on the veins ( Fig. 3 D); length 1.65–1.71 (mean = 1.67). Legs pale brown; trochanter pale; femur and tibia pale brown with brown spots and tibia brown distally; pretarsus brown ( Fig. 3 D). Abdomen: length 0.90–1.01 (mean = 0.93), width 1.51–1.98 (mean = 1.69). Abdomen with eleven–twelve dark tubercles with one seta in the apex and numerous small, hyaline tubercles scattered on the dorsal surface of abdomen.

Figures

FIGURE 1. General aspect. X. gracilis ♂, dorsal view (A – B); X. picturatum ♂, dorsal view (C); X. gracilis ♀ dorsal view (D – E).

FIGURE 2. Male genitalia. X. gracilis. Genital capsule in situ (A), genital capsule (B), pygophore (C), male phallus (D), paramere (E). L lo: lateral lobe; M lo: medial lobe; Pa: paramere; Pa lo: Paralateral lobes.

FIGURE 3. Nymphal stages. X. gracilis, dorsal view; second instar (A), third instar (B), fourth instar (C), fifth instar (D). scale line: 1 mm.