Limnocoris pallescens ( Stål, 1861 )

Rodrigues, Higor D. D. & Sites, Robert W., 2023, Notes on the morphology of two species of Limnocoris Stål (Heteroptera: Naucoridae) from South America, Zootaxa 5264 (1), pp. 137-142 : 138

Limnocoris pallescens ( Stål, 1861)

( Figs. 1–2 )

Discussion. Wing polymorphism in adults of Heteroptera is common and the adult may have the fore- and hindwings well-developed or have some degree of reduction in both pairs of wings or in only one pair. In Limnocoris , in general, the forewing is not reduced, but varying degrees of suppression of the clavus, claval suture, intraclaval suture, and posterior suture of the embolium can occur ( Fig. 1 ). The hemelytral membrane is usually not reduced, although this may occur in some species, as L. abbreviatus Montandon , L. decarloi Nieser & López-Ruf , L. longirostris Rodrigues & Sites , and L. moapensis (La Rivers) . Because individuals with some degree of hindwing reduction probably have limited or no ability to fly, the thoracic musculature of these specimens also has some degree of reduction, as was verified for the Palearctic species Ilyocoris cimicoides (Linnaeus) ( Larsén 1970) . The external morphology of some structures, most notably the pronotum and embolium, is associated with this musculature reduction; thus, the appearance of these structures can differ depending on the wing condition.

In the revision of Limnocoris associated with the foothills and slopes of the Andes, Rodrigues & Sites (2021) examined brachypterous and macropterous specimens of L. pallescens . In the macropterous form, the posterolateral corner of the pronotum is more broadly rounded, the posterior margin of the pronotum is sinuous, the curvature of the embolium lateral margin near the humeral angle is approximately 37 degrees, and the claval, intraclaval, and posterior embolar sutures are well-developed ( Fig. 1F ), whereas in the brachypterous form, the posterolateral corner is narrowly rounded, the posterior margin of the pronotum is shallowly concave medially, the curvature of the embolium lateral margin near the humeral angle is approximately 45 degrees, and the claval, intraclaval, and posterior embolial sutures are usually absent ( Fig. 1D ), although the claval and/or intraclaval sutures may be present but suppressed in some specimens (as in Fig. 1E ). Another difference between the two wing forms studied by Rodrigues & Sites (2021) is the pair of posterior indentations in the pronotum, present only in the macropterous specimens. These indentations are located laterally to the posterior, dark-brown transverse sulcus of the pronotum, and are probably associated with the pleural apodemes (see Parsons 1967, 1968) that support the origins of thoracic musculature ( Fig. 1F ).

In the present study, we examined brachypterous specimens of L. pallescens from the states of Monagas and Sucre, northern Venezuela. In these specimens, the pronotum and embolium are shaped differently in comparison to the brachypterous specimens examined by Rodrigues & Sites (2021). Specifically, the posterolateral corner of the pronotum is acute, the posterior margin of the pronotum is straight and without a median concavity, and the embolium has greater curvature (approximately 60 degrees) near the humeral angle ( Figs. 1A, C ). We also verified the hindwing sizes of the two brachypterous forms. In the specimens examined from Monagas and Sucre, the hindwing reaches to only the anterior margin of abdominal tergum II, whereas in the brachypterous specimens examined by Rodrigues & Sites (2021), the hindwing extends to slightly beyond the anterior margin of abdominal tergum III ( Fig. 1E ). Similar variation in these structures can be found in other species in which brachypterous and macropterous forms are known.

The diagnostic characteristics of the species in the material examined here and that studied by Rodrigues & Sites (2021) are similar: shape of the meso- and metasternal carinae ( Fig. 1G ), the propleuron shagreened area with posterior end weakly angulate ( Fig. 1B ), and the posterior margin of the female subgenital plate rounded ( Fig. 1H ); thus, we consider all these specimens to belong to L. pallescens . As such, L. pallescens is now known to have two brachypterous forms.

Published records. Colombia ( Stål 1861). Venezuela: Aragua, Carabobo, and Vargas ( Montandon 1898; Rodrigues & Sites 2021).

Distribution. This species is distributed in Colombia and Venezuela, northern South America. The Colombian record, which represents the type locality of L. pallescens , does not have precise data, as only the name of the country was given in the original description. The previously reported records from Venezuela were concentrated in the central portion of the Coastal Range, a mountain range system near the Caribbean coastline. The specimens examined in the present study, which represent new distribution records, were collected in the eastern portion of the Venezuela Coastal Range, in the states of Monagas and Sucre ( Fig. 2 ).

Material examined. COLOMBIA: HOLOTYPE of L. pallescens, Columbia [= COLOMBIA]/ Dohrn / Typus / NHRS-GULI 000008904 (♀ brachypterous NHRS). VENEZUELA, Aragua: Carretera , Maracay-Choroní , Sector los Cerritos , 18–19.IX. 2004, 200 m/ Collector J. Camacho (1♀ brachypterous MZUSP); Choroní , Los Cerritos , 200 m, 17.XI.2005, J. Camacho col. (1♁ brachypterous MZUSP); Henri Pittier National Park , Río Cumboto , 10.39376°N, 67.79597°W, 4 January 2009, 130 m, leaf packs & kick netting, leg. A. Short, VZ09-0104-02A (1♀ macropterous, 1♀ brachypterous UMC). Monagas: Monagas bor., Cueva del Garcháro cave env. (ca. 10 km W of Caripe), 21-22 Feb. 2005 / Venezuela 2005 Exp., GPS (??? N11 o 48’15.3”, W62 o 06’57.4” ???), Janšta P. & Musilová Z. lgt. (2♁, 1♀ NMPC; 1 ♀ UMC; all brachypterous). Sucre: El Yaque near Mt. Turumquire , Sucre, Venez., G. Netting/ Jan.8 1930 (5♁ CMNH; 1♁ UMC; all brachypterous).

Figures

FIGURE 1. Limnocoris pallescens (Stål), (A) dorsal and (B) ventral habitus of brachypterous male from Sucre (CMNH), white arrow indicates pronotum posterolateral corner, shagreened area of propleuron highlighted, (C) dorsal habitus of brachypterous male from Monagas (UMC), (D) dorsal habitus of holotype brachypterous female from Colombia (NHRS), (E) dorsal habitus of brachypterous female from Aragua (MZUSP) with part of right hemelytron removed, white arrow indicates suppressed intraclaval suture, (F) dorsal habitus of macropterous female from Aragua (UMC), white arrow indicates rounded posterior indentation, (G) part of thorax in ventral view, meso- and metasternal carinae highlighted, specimen from Monagas (UMC), (H) terminal abdominal sterna of female from Monagas (UMC), subgenital plate highlighted; dotted lines in figures A, D and F indicate angle measured on the embolium. cs = claval suture, em = embolium, hw = hindwing, is = intraclaval suture, ms = mesosternal carina, mt = metasternal carina.

FIGURE 2. Distribution records of Limnocoris pallescens (Stål) in Venezuela.