Ambrysus maya Sites and Reynoso

Sites, Robert W. & Reynoso-Velasco, Daniel, 2015, Review of the Ambrysus stali La Rivers species complex (Heteroptera: Nepomorpha: Naucoridae) with the description of a new species from Mesoamerica, Zootaxa 4018 (2), pp. 279-291 : 282-285

Ambrysus maya Sites and Reynoso , NEW SPECIES

( Figs. 1 , 3–4 )

Description. Macropterous male. HOLOTYPE, length 7.84; maximum width 4.40. Paratypes (n = 2), length 7.84–7.92 (mean = 7.88); maximum width 4.32–4.52 (mean = 4.42). General shape fusiform; widest across abdominal segment III ( Fig. 3 A). Overall dorsal coloration anteriorly pale yellow with dark brown pattern on forelegs, head, and pronotum ( Fig. 3 A); anterior pale yellow has greenish tone in live specimens ( Fig. 4 B); posteriorly with dark brown scutellum and hemelytra. Exposed connexiva with alternating creamy white and dark checkered appearance. Dorsal surface coarsely punctate. Ventrally, mostly brown, lighter centrally.

Head. Head length 1.36; maximum width 1.98. Eyes convergent, synthlipsis 0.72; thin band of cuticle posterior to eye; eyes flat and not raised above level of vertex, slightly raised above level of pronotum. Anterior margin between eyes convex, extending anteriorly in front of eyes 7% of head length; posterior margin between eyes strongly convex, extending posteriorly 30% of head length. Labrum width 1.8 x length, evenly rounded. Labium brown, with three visible segments, extending 0.48 beyond labrum. Antennal segment proportions 2:9:11:6, length 0.54, elongate hairs on segment 4 and distal 2/3 of 3.

Thorax. Pronotum mostly pale yellowish brown with dark brown punctures, anteromedial brown maculation, irregular longitudinal brown stripes, some longitudinal stripes enhanced with dark punctures; slightly rugose; lateral margins convex; sparse erect setae; explanate, strongly convergent anteriorly; posterior margin nearly straight; anterior margin deeply concave receiving convex posterior margin of head; transverse line of punctures defining anterior margin of band in posterior 1/4; posterolateral corners obtuse, rounded; width 3.2 x length; length at midline 1.22; maximum width at posterolateral corners 3.92. Prothorax ventrally brown and pruinose medially, with yellow glabrous lateral band; apices of propleura meeting broadly at midline, separated from level of prosternellum. Probasisternum brown, with sharp medial carina and generally appearing pruinose, row of elongate pale hairs lateral to carina. Prosternellum light brown, extending beneath apices of propleura. Elongate setae along posterior margin of propleuron. Scutellum mostly brown with yellow anterior corners and apex, triangular, densely punctate, width 1.9 x length, width 2.60, length 1.36. Hemelytra densely punctate. Claval commissure length 0.72. Embolium length 2.30, greatest width 0.62; lateral margin slightly convex in proximal half, more pronounced in distal half. Hind wings well developed. Mesobasisternum with midventral longitudinal tumescence with sulcus on midline; tumescence terminating posteriorly as acute mesosternellum. Metasternellum (=metaxyphus) transverse, subtriangular, with apex acute.

Legs. All leg segments pale yellowish brown, darker distally on fore and hind legs. Profemur pale yellowish brown with dark brown along anterior margin continuous to apex; dark brown posterior marking extending anteriorly, becoming discontinuous where it approaches or meets anterior margin dark marking; row of 10–12 combs of short brown spines in basal half of posterior margin; anterior margin with dense pad of setae without associated spines. Protibia and tarsus with inner surface flattened and with spatulate setae; tarsus immovable, onesegmented; pretarsal claw single, minute, triangular. Procoxa with dark brown basal marking on lateral to anterior surfaces, cluster of stout brown anteromedial spines. Mesocoxa partially recessed into thorax. Metacoxa with longitudinal sulcus that can accommodate flexed metafemur. Meso- and metafemora with row of short, brown spines on anterior margin; spines restricted to basal 1/3 and single on mesofemur, combs of 1–4 spines irregularly spaced along full length of metafemur. Mesotibia with ventrolateral, ventromedial, dorsolateral, and dorsomedial rows of stout reddish-brown spines, dorsolateral and dorsomedial rows include combs of up to 4 spines; stout spines at apical rim dorsally, two transverse rows of stout spines at apex of ventral margin. Metatibia with ventrolateral, ventromedial, dorsolateral, and dorsomedial rows of stout reddish-brown spines, transverse rows of stout spines at apex of ventral margin. Meso- and metatibiae and -tarsi with long, pale swimming hairs; hairs sparse on mesotibia and -tarsus, profuse on metatibia and -tarsus. Meso- and metapretarsi with paired claws slender, curved in distal half, with basal tooth. Leg measurements as follows: foreleg, femur 1.86, tibia 1.60, tarsus 0.32; middle leg, femur 1.88, tibia 1.64, tarsomeres 1–3, 0.10, 0.28, 0.36; hind leg, femur 2.32, tibia 2.72, tarsomeres 1– 3, 0.16, 0.52, 0.47.

Abdomen. Abdomen dorsally with connexiva of III–VII exposed and with checkered appearance ( Fig. 4 B), posterior half of III–VII dark brown, anterior half of III–V creamy white and of VI–VII brown; VIII mostly brown; lateral margin with row of pale setae, group of trichobothria on dorsal surface near posterolateral corners. Posterolateral corner of III slightly acuminate, IV–VII spinose. Accessory genitalic process of VI broad, apical margin flattened with corners broadly rounded, broadly prolonged laterally ( Fig. 3 B). Medial lobes of VIII (pseudoparameres) with apical corners rounded, distal margin flat ( Fig. 3 D). Ventrally mostly brown laterally, brownish yellow medially, pruinose, with pile of fine hairs. Laterosternites III–VI with yellow near middle of lateral margin. Lateral margin with thin glabrous band. Glabrous patches on laterosternites II–VII. Mediosternite V with posterior margin slightly asymmetrical. Phallosoma with left ventral lobe reflexed dorsad, unarmed with teeth; right ventral lobe appressed to body of phallosoma, unarmed ( Fig. 3 C). Parameres subquadrate, pedunculate, symmetrical, mesal margin slightly convex with corners broadly rounded ( Fig. 3 E). Pygophore with anterior margin between parameres slightly produced at midline, posterior apex with fine setae.

Macropterous female. Paratypes (n = 11), length 7.68–8.96 (mean = 8.45); maximum width 4.36–4.72 (mean = 4.55). Similar to male in general structure and coloration except as follows: Mediosternite V symmetrical. Mediosternite VII (subgenital plate) with medial convexity and distolateral production ( Fig. 3 F). Laterosternite VI with posteromedial corner on left side produced into well-developed spine directed posteroventrad, posteromedial corner on right side produced, tuberculate, deflexed ventrad.

Diagnosis and comparative notes. This species can be distinguished from other members of the species complex by the significantly narrower fore femora (t=3.803, df=15, p=0.002) and its noncoincident geographic range. It can be distinguished from all other naucorids in Mesoamerica by its small size, fusiform body shape, and dark longitudinal markings of the pronotum and dark markings on the dorsal surface of the profemora.

Habitat description. At the type locality, specimens were collected from marginal vegetation including dead leaves, grasses, and other vegetation ( Fig. 4 A). The river was shallow (ca. 1 m) with cobble substrate and swift current. In the riffles were the naucorids Ambrysus circumcinctus Montandon and Limnocoris insularis Champion , and the byrrhoid beetles Helichus suturalis LeConte (Dryopidae) , Phanocerus clavicornis Sharp , Xenelmis bufo (Sharp) , Heterelmis sp., Hexacylloepus sp., and Microcylloepus sp. ( Elmidae ). Specimens of Ambrysus maya from the Sibun River in Belize were collected mostly from vegetational debris caught on branches or along the margins. Other insect species in the Sibun River included Argia sp. ( Coenagrionidae ); Laccophilus oscillator laevipennis Sharp , L. proximus Say (Dytiscidae) ; Anopheles albimanus Wiedemann , and Chagasia bathana (Dyar) (Culicidae) (R. Vogtsberger, pers. com.).

Discussion. Although the Central American countries south of Guatemala have been well-collected and the fauna studied by many scientists over the past century beginning with Champion (1901), A. maya has not been reported from there. Thus, this species appears to be widely separated from A. tricuspis in Colombia, the nearest known member of the A. stali complex ( Fig. 1 ). The majority of insects in Central America are suggested to have originated from taxonomic elements of northern South America ( Kimsey 1992). Ambrysus maya follows this pattern since most of the diversity of this species complex is distributed throughout the Guyana Shield region with a single incursion into Mesoamerica. Alternatively, the ancestor of this complex might have moved southward from the Mexican geographic center of Ambrysus diversity, and subsequently became discontinuous with the current species through vicariance. Substantially more geological time for either scenario to have occurred than was previously considered was shown recently. Montes et al. (2015) provided evidence that the Central American land bridge formed in the Miocene epoch 10–12 million years earlier than the 3 million year Pliocene model that had been widely accepted. Moreover, a phylogenetic analysis of New World naucorid groups with attention to divergence times may be able to evaluate invasion patterns. The diversity of Ambrysus is greatest in North America and of Cryphocricos and Limnocoris in South America.

Etymology. The specific epithet is a noun in apposition in reference to the Maya civilization, which occupied this region of Mesoamerica until the 17th century.

Repositories. The holotype and some paratypes are deposited in the Enns Entomology Museum (University of Missouri); additional paratypes are deposited in Midwestern State University (Wichita Falls), Universidad del Valle de Guatemala ( Guatemala City), Universidad Nacional Autónoma de México ( Mexico City), and the United States National Museum of Natural History (Washington D.C.).

Type material examined. HOLOTYPE ♂: BELIZE: Orange Walk District: Río Bravo ca. 10 mi. N. of Gallon Jug at Cedar Crossing, 19 April 2014, 44 m, 17°41.415´N, 89°01.615´W, R. Sites & W. Shepard, vegetated margins, L-1740; PARATYPES: same data as holotype (1♀); Belize District: Sibun River, 17º24.690'N, 088º25.288'W, 1 VII 2009, bamboo & branches, coll J. H. Adams (1♀); same data except 17º24.281'N, 088º26.012'W (1♀); same data except 17º24.702'N, 088º25.297'W (1♂); same data except 17º16.112'N, 088º34.276'W, 29 VI 2009, submerged stones (1♀); Cayo District: Sibun River, 0338582N, 1916372W, detritus patch, 26–30 VI 2009, coll J. H. Adams (1♀); same data except 0333330N, 1912078W (1♀); same data except 0348708N, 1925658W (1♀); same data except 0338622N, 1916554W (1♀); same data except 033283N, 1911970W (1♀). GUATEMALA: Alta Verapaz: Lag[una]. Lachua, 19 VII 1995, J. C. Schuster (1♀). MEXICO: Chiapas: Chajal Arroyo Manzana, 9-XII-2008, G. Mendez / Colección del Instituto de Biología, UNAM México, D.F. (1♀); Tabasco: Río Carrizal, Est. No. 7, 10-VI-1996, 17º57.23'N, 93º07.17'W, J. Bueno, A. Contreras, R. Barba / Colección del Instituto de Biología, UNAM México, D.F. (1♂).

Figures

FIGURE 1. Distribution of species in the Ambrysus stali species complex.

FIGURE 3. Structures of Ambrysus maya n. sp. (A) dorsal habitus of holotype, (B) 6 th and 7 th abdominal terga of male, (C) ventral and left sides of phallosoma, (D) 8 th abdominal tergum showing medial pseudoparameres, (E) male pygophore with paired parameres (phallosoma removed), (F) terminal abdominal sterna of female showing subgenital plate (setae have been removed to reveal shape).

FIGURE 4. Ambrysus maya n. sp. (A) Río Bravo, the type locality with habitat inset, (B) live specimen in Río Bravo.