Placomerus obscuratus Sites & Camacho

Sites, Robert W. & Camacho, Jesús, 2014, Neotropical genera of Naucoridae (Hemiptera: Heteroptera: Nepomorpha): New species of Placomerus and Procryphocricos from Guyana and Venezuela, Zootaxa 3753 (5), pp. 469-482 : 471-474

Placomerus obscuratus Sites & Camacho , NEW SPECIES

Figs. 2–5

Description. Brachypterous male. HOLOTYPE, length 6.08; maximum width 3.76. Paratypes (n = 10), length 6.08–6.80 (mean = 6.30); maximum width 3.68–4.00 (mean = 3.74). Ovate. Dorsally, overall coloration light brown anteriorly with dark brown wings; glossy and punctate throughout ( Fig. 2 ). Ventrally, mostly yellowish brown. Head, pronotum, scutellum, and hemelytra sparsely covered with fine setae.

Head. Length 1.16, maximum width 2.20; inner margin of eyes distinctly concave; synthlipsis at anterior margin 0.94, interocular distance at posteromesal corners 1.06; head margin laterad of eye narrow, widening anteriorly; yellowish brown with scattered brown punctation, series of dark brown punctures paralleling inner margin of eyes especially pronounced in basal half; labrum subtriangular, apex broadly rounded, 1.65 times as wide as long; antennal proportions 3:9:11:6.

Thorax. Pronotum broad, 2.3 x as wide as long, length at midline 1.40; maximum width at posterolateral corners 3.20; transverse, impunctate band in posterior ¼ along margin set off by irregular row of distinct punctures; anterior 3/4 with many small shallow brown punctures; sparsely scattered, distinct larger dark punctures; laterally with narrow rim set off by groove with punctures; lateral margins gently convex, convergent anteriorly; posterolateral corners rounded; posterior margin shallowly convex. Ventrally yellowish brown coloration becoming dark brown near mesal margin of propleuron; patch of stout setae on dark marking of propleuron at base of coxa. Scutellum with many small, light colored punctures; irregularly mottled with yellow and brown; apex yellow; triangular with shallowly sinuate posterolateral margins, 1.8 x as wide as long, width 1.90, length 1.06. Hemelytra dark brown with subtle reddish mottling, with many small, light colored punctures. Clavus 4.2 x as long as wide, length 2.60, width at middle of scutellum 0.62. Claval commissure locking mechanism length 0.62.

Embolium length 2.04 (chord measurement), greatest width 0.64; strongly widened in distal half; lateral margin evenly convex; yellowish brown in anterior 2/3, brown posteriorly. Meso- and metasterna mostly pruinose. Hindwing extending posteriorly to middle of abdominal tergum II. Mesosternum with midventral tumescence and elongate setae.

Legs. Coxa, trochanter, femur, tibia yellowish brown; tarsus, pretarsus darker. Mesotrochanter with heavy brush of light colored hairs along posterior surface. Mesofemur width 35% that of length; with posteroventral row of 34–38 stout, single brown spines; spines subequal from base to near apex, penultimate spine elongate, distal spine slightly shorter than penultimate spine; comb of 6–7 stout hairs distad of spines; posterodorsal margin extended posteriorly and with heavy brush of light colored hairs beginning at apex of trochanter, extending for ca. half length of femur. Mesotibia width 32% that of length. Meso- and metatibia short, stout, with stout reddish brown elongate spines. Meso- and metapretarsal claws elongate, gently curved. Leg measurements as follows: foreleg, femur 1.48, tibia 0.68, tarsus 0.40, pretarsal claw 0.38; middle leg, femur 1.42, tibia 0.86, tarsomeres 1–3 0.10, 0.34, 0.34; hind leg, femur 1.64, tibia 1.42, tarsomeres 1–3 0.12, 0.64, 0.54, pretarsal claw 0.42.

Abdomen. Lateral margins smooth; with fine, light-colored hairs on III-VIII. Posterolateral corner of segment II square, III produced, IV-VII spinose. Ventrally golden brown, darker laterally, with fine pile of short setae throughout and sparse, scattered elongate setae, and dense mid-ventral band of light colored hairs beginning on VI, continuing to posterior margin of abdomen. Posterior margin of mediosternite III, IV straight, V deeply incised medially, VI asymmetrical with medial convexity and dextral concavity.

Male genitalia. Aedeagus slender, elongate, laterally compressed, gently arcuate to left, apex broadly rounded to slightly acuminate ( Fig. 3 ). Parameres slender, elongate, longitudinally concave, asymmetrical, left overlapping right apically, each with 3 lobes, dorsal and ventral surfaces with sparse setae ( Fig. 4 ). Pygophore with margin between parameres strongly convex and rounded ( Fig. 3 ), with fine setae.

Brachypterous female. Size (n = 10): Length 6.16–6.84 (mean = 6.40); maximum width 3.76–4.24 (mean = 3.93). Coloration and setation generally same as for male. Otherwise: Mediosternites III–VI with posterior margin straight. Subgenital plate with middle third glabrous, broadly triangular with apex narrowly rounded, apical ¼ abruptly narrowed ( Fig. 5 ), longitudinally strongly concave such that apex nearly semicircular in posterior view, width 1.12 mm, length 0.96 mm.

Macropterous male. (n = 2). Length 5.76–6.40 (mean = 6.08); maximum width 3.72–4.00 (mean = 3.86). Coloration, setation, pronotum proportions, posterolateral corners of pronotum, scutellum proportions generally same as for brachypterous male. Otherwise, clavus and claval commissure correspondingly longer: Clavus 4.7 x as long as wide, length 2.60; width at middle of scutellum 0.60; claval commissure locking mechanism length 0.68. Hindwing extending to middle of tergum VIII.

Macropterous female. (n = 2). Length 6.56; maximum width 3.92–4.00 (mean = 3.96). Coloration, setation, pronotum proportions, posterolateral corners of pronotum, scutellum proportions generally same as for brachypterous female. Otherwise, clavus and claval commissure correspondingly longer: Clavus 5.0 x as long as wide, length 3.12; width at middle of scutellum 0.62; claval commissure locking mechanism length 0.72. Hindwing extending to middle of tergum VIII.

Diagnosis and comparative notes. We compared this new species with the holotype of P. micans at the California Academy of Sciences and with paratypes from the United States National Museum of Natural History, Essig Museum of Entomology at the University of California - Berkeley, and Snow Museum at the University of Kansas. An additional paratype in the British Museum of Natural History was examined but not used for comparison. Both species appear highly polished. P. obscuratus can be distinguished from P. micans by the narrower clavus, which ranges in length/width from 4.2 to 5.0 mm when considering both sexes and wing morphs; whereas the P. micans paratypes ranged from 3.1 to 3.9 (all with brachypterous hindwings). In the P. micans paratype at USNM ( Fig. 1 ), the clavus is noticeably wider than in the other P. micans paratypes that we have examined; however, all are proportionately wider than in all specimens of P. obscuratus . In addition, the interocular distance measured at its widest point in comparison with maximum head width is significantly smaller in P. obscuratus [t(23) = 9.17, p <0.0001]. Specifically, interocular distance/head width averaged 0.53 in P. obscuratus and 0.57 in P. micans . The hemelytra are substantially darker in P. obscuratus . The posterolateral margins of the scutellum are nearly straight in both wing morphs of P. obscuratus and concave in P. micans . The aedeagus and parameres appear quite similar in both species, although the apex of the aedeagus is truncate in the two paratypes of P. micans from which we extracted genitalia, whereas it is broadly rounded to slightly acuminate in P. obscuratus .

Discussion. Hindwing polymorphy with brachypterous and macropterous forms occurs in various genera of Naucoridae (e.g., Ambrysus and Limnocoris in the New World and many others in the Old World) whereas length of the forewings is largely unaffected. Placomerus micans is known only from hindwing brachypterous individuals from southern South America. However, this new species is represented by brachypterous and macropterous individuals, with both forms co-occurring in some populations. Specimens from the type locality in Guyana are predominantly brachypterous, whereas most of the specimens examined from various localities in Venezuela are macropterous. Unlike most other genera with hindwing brachyptery, associated differences in development of the posterolateral corners of the pronotum and diminishment of the clavus are not seen in P. obscuratus , although these features are apparent in the congener P. micans .

Habitat description. Paul Spangler's field notes included the following information about the type series collection in Guyana: "seepage pools beside airstrip & at falls." Spangler also noted animal associates with the type series collection: " Laccophilus , veliids: Microvelia ayacuchana & Microvelia sp.", and a separate quantified listing: " Microvelia -192, gerrids-16, corixids-2, naucorids-58, Laccophilus -16, Paracymus -1, fish-3, weevil-1." The Venezuelan specimens were collected from grassy flooded areas, an isolated forest pool in a streambed, a rock pool, pool in culvert, and shallow backwaters.

Etymology. The specific epithet obscuratus is in reference to the darkly colored hemelytra and scutellum in comparison to those of the congener P. micans .

Repositories. The holotype and some paratypes are deposited in the United States National Museum of Natural History. Additional paratypes are deposited in Universidad del Zulia, Maracaibo; Museo del Instituto de Zoologia Agrícola, Maracay; Naturhistorisches Museum, Vienna; Snow Entomological Museum Collection, Lawrence; and University of Missouri, Columbia.

Type material examined. HOLOTYPE, brachypterous ♂: GUYANA: Kaieteur Falls, 0 5o 10’N, 59o 28’W, 357 m, 7 Apr 1994, PJ Spangler, #20. PARATYPES: same data as holotype (18 brachypterous ♂, 14 brachypterous ♀, 2 macropterous ♂, 2 macropterous ♀). VENEZUELA: AMAZONAS: river nr. Orinoco/Sipapo confl., 5o 03.707’N 67o 46.768’W, 92 m, 15 January 2009, expedition team, VZ09-0115-01A, in/along river (1 macropterous ♀); same data, shallow backwaters, leg. A. Short, VZ09-0115-01C (1 macropterous ♂); same data, leg. M. García, VZ09-0115-01D, rock pool (1 macropterous ♀); S. Communidad Porvenir, 5o 0.514’N 67o 45.315’W, 87 m, 15 January 2009, leg. Short & García, VZ09-0115-03A, pool in culvert (1 macropterous ♀); nr. Iboruwa, "Tobogancito", 5°48.414'N, 67°26.313'W, 80 m, 13.i.2009, leg. A. Short et al., VZ09-0113- 02X (2 macropterous ♂). APURE: ca. 6 km S. Rio Cinaruco Morichal and marsh, 6o 30.900’N 67o 32.604’W, 8 January 2006, AS-06- 0 19, leg. A.E.Z. Short (1 macropterous ♂, 2 macropterous ♀). BOLÍVAR: Los Pijiguaos, 6o 35.617’N 66o 49.238’W, 80 m, outcrop/morichal, 12 January 2009, leg. García, Short, & Miller, VZ09-0112-01D, isolated forest pool in streambed (5 macropterous ♂, 4 macropterous ♀); same data, but algae on rocky margin of morichal, VZ09-0112-01B (2 macropterous ♂, 3 macropterous ♀); same data but morichal, VZ09-0112- 01X (5 macropterous ♂, 8 macropterous ♀); ca. 20 km E. Maripa, 7o 26’ 23.2”N 64o 57’ 5.6”W, 45 m, 5 August 2008, leg. A. Short & M. García, grassy flooded area, AS-08-074 (1 macropterous ♂).

Other material examined. VENEZUELA: AMAZONAS: 15 km S Puerto Ayacucho, 5°30.623'N, 67°36.109'W, 110 msnm, 14/I/2009, J. Camacho, A. Short, M. García, L. J. Joly y L. Miller, colectores, VZ09- 0114-03A ( MALUZ, 1 macropterous ♀); ca. 15 km S. Puerto Ayacuho, nr. Campamento Canturama, 5°30.623'N, 67°36.109'W, 110 m elev, 14.i.2009, Short, small seep connecting pools, VZ09-0114-03B ( MALUZ, 1 macropterous ♀); rio cerca confluencia Rios Orinoco y Sipapo, 5°03.707'N, 67°46.768'W, 92 msnm, 15/I/2009, J. Camacho, A. Short, M. García, L. J. Joly y L. Miller, colectores, VZ09-0115- 01X ( MALUZ, 7 macropterous ♂, 9 macropterous ♀); Mcpio Atabapo, San Fernando de Atabapo, 350 m, 06-08/IX/1996, 4°02'30"N, 67°42'15"W, colector J. Camacho, trampa luz eléctrica ( MALUZ, 1 macropterous ♀). APURE: 9/I/2006, colectores: J. Camacho, M. García, A. Short ( MALUZ, 4 macropterous ♂, 4 macropterous ♀); road between Rio Orinoco and Rio Cinaruco, 17.i.2009, 6°30.900'N, 67°32.604'W, 68 m elev, Short, Miller, Camacho, Garcia, Joly, Morichal margin, VZ09-0117- 01X ( MALUZ, 1 macropterous ♂, 6 macropterous ♀). BOLÍVAR: La Gran Sabana, San Francisco de Yuruani, August 2008 / A. Short, M. García, L. Joly colectores, 0 5o 03’ 21”N 61o 05’ 54”W ( SEMC, UMC, MALUZ, 1 macropterous ♂, 8 brachypterous ♂, 1 brachypterous ♀); 25 km al E de El Burro, 6°13´4.6"N, 67°14´26.4"W, 60 msnm, 13/I/2009, VZ09-0113-01 ( MALUZ, 1 macropterous ♂, 2 macropterous ♀). GUARICO: San Nicolasito Field Station, Rio Aguaro, 8°6.226'N, 66°26.228'W, 52 m elev, 10.i.2009, Short, García, Camacho, Miller, Joly, along river VZ09-0110-01A ( MALUZ, 2 macropterous ♂, 2 macropterous ♀).

Figures

FIGURES 1 – 2. Hindwing brachypterous PARATYPES of Placomerus. (1) Placomerus micans collected in Paraguay, housed at USNM, (2) Placomerus obscuratus n. sp. collected in Guyana, housed at USNM.

FIGURES 3 – 5. Features of Placomerus obscuratus n. sp. (3) male genital capsule with aedeagus and parameres (4) left and right parameres in lateral view (5) terminal abdominal sterna of female paratype including subgenital plate. Sizes are not proportionate among figures.