Ambrysus quadracies La Rivers, 1976

Reynoso-Velasco, Daniel & Sites, Robert W., 2025, Revision of the Ambrysus signoreti Stål species complex (Heteroptera: Naucoridae: Ambrysinae). Section 3., Zootaxa 5735 (1), pp. 1-66 : 39-41

Ambrysus quadracies La Rivers

( Figs. 23–25 )

Ambrysus quadracies La Rivers 1976 : Biol. Soc. Nev. Occas. Pap., 41: 3–4 (original description).

Supplemental description. Female. Mediosternite VII (SGP) asymmetrical, left margin with small and ventrally deflexed lobe at mid-length; right margin without lobe; posterolateral corners pointed; central lobe clearly concave medially, giving the appearance of two pointed lobes, almost at same level as posterolateral corners ( Fig. 23B ).

Male. Accessory genitalic process of tergum VI (AGP) curved to right at approximately 20 degrees close to proximal third, angled again at approximately 70 degrees at distal third ( Fig. 23C ). Medial lobes of tergum VIII (pseudoparameres) symmetrical, posterolateral corners narrowly rounded, posteromesal corners broadly rounded, posterior margin almost straight ( Fig. 23D ). Phallosoma elongate, linear, slender, broadly rounded dorsoapically; left endosomal sclerite broad, plate-like, with oblique row of small denticles; right endosomal sclerite small, lightly sclerotized, with few denticles ( Fig. 23E ). Parameres symmetrical, as long as maximum width, mesal margin convex. Proctiger almost as long as width at base. Pygophore with elongate setae sparsely distributed over most of surface, with thick brush of elongate setae on posterior margin ( Fig. 23F ).

Diagnosis. This species can be distinguished from others in this section by the asymmetrical SGP with a ventrally deflexed small lobe on the left margin. Additionally, the posterolateral corners are pointed and the central lobe is clearly concave medially, giving the appearance of two pointed lobes ( Fig. 23B ). Also, males exhibit the phallosoma broadly rounded to truncate dorsoapically, left endosomal sclerite plate-like with a few small denticles, and right endosomal sclerite inconspicuous with few small denticles ( Fig. 23E ). Furthermore, both sexes exhibit the posterolateral corners of abdominal segments III–V strongly produced, robust, and spinose ( Figs 23A ).

Comparative notes. Other species in this complex also exhibit spinose posterolateral corners of abdominal segments III–V, but only those of A. inflatus La Rivers (Section 2) are as robust and strongly extending posteriorly as the corners of A. quadracies .

Discussion. This species measures 9.37–12.25 in length and 6.87–8.12 in width. At the time of the description, La Rivers (1976) considered the posterior margin of the SGP of this species to be similar to that of his A. rotundus La Rivers. The four-pointed posterior margin is similar in both species; nonetheless, the central lobe of A. quadracies is deeply concave medially, giving the appearance of two pointed lobes, and in A. rotundus (= A. signoreti ) it is only shallowly concave, giving the appearance of two rounded lobes. Although not mentioned by La Rivers, the lateral lobe on the left margin of the SGP is similar in both species. Recent phylogenetic studies ( Reynoso-Velasco & Sites 2021, Sites 2022) suggest that A. quadracies is sister to a clade including A. lunatus and A. signoreti + A. sitesi .

In the original description, La Rivers stated that the female holotype and the allotype (ergo a male) were part of the collection at Instituto de Biología ( CNIN), while an additional female paratype was to be deposited in the collection of the Biological Society of Nevada (currently in the CAS). The specimen in the CNIN labeled as the allotype is actually a female and the additional paratype in the CAS is a male. These two specimens were probably mislabeled by La Rivers .

Variation. Some females exhibit the SGP with the margin of the lateral lobe unsclerotized, sinuous, and not deflexed ventrally. Also, the posterolateral corners can be right-angled.

Type locality. Mexico: Veracruz: Mpio. Catemaco, Catemaco .

Repository. Female holotype ( Fig. 24 ) is housed at the CNIN.

Published records: MEXICO: Chiapas, Oaxaca, Veracruz ( La Rivers 1976; Reynoso-Velasco & Sites 2018b, 2019b; Reynoso-Velasco 2021a).

Distribution. This species is distributed in the southern Mexico lowlands (majority of records below 200 meters) of the states of Chiapas, Oaxaca, and Veracruz ( Fig. 25 ). All records are within the southern section of the Veracruzan biogeographic province. In the state of Chiapas, numerous specimens of this species were collected alongside or in the vicinity of the border with Guatemala and in some cases from rivers that originate in that country. Thus, this species clearly also occurs in Guatemala. Three female specimens of A. quadracies in the CNIN (2) and IEXA (1) have labels indicating they were collected in Cuernavaca, Morelos (see Material examined), which is 300 km northwest of the closest records in northern Oaxaca (L-1880, L-1881) and separated from the others presented here by the eastern section of the Sierra Madre del Sur mountain range. Thus, we consider it is doubtful that this species occurs in the state of Morelos; probably, the three female specimens were mislabeled.

Type material examined. HOLOTYPE ♀ (by original designation). MEXICO: Veracruz: [Mpio. Catemaco], Catemaco / 10-VI-1964, L. Vázquez / Ambrysus quadracies Holotype ♀. PARATYPES: same data as holotype but / Ambrysus quadracies Allotype ♂ [incorrectly labeled as a male] ( 1♀ CNIN); same locality data but / Ambrysus quadracies Paratype / Ira La Rivers Collection bequeathed to the California Academy of Sciences - 1978 ( 1♂ CAS) .

Additional material examined. MEXICO: Chiapas: Mpio. Frontera Comalapa, Río Grijalva at El Caracol , 8 km S of Frontera Comalapa, 15°36’07.0’’N, 92°09’14.5’’W, 677 m, 31-Mar-2015, L-1897, Reynoso-Velasco, Sites, Shepard & Barr colls. ( 13♂, 15♀ IEXA) ; Mpio. Ixtacomitán, Ixtacomitán, Balneario Río Blanco , 17º25’21.8’’N, 93º06’08.6’’W, 106 m, 17-May-2012, L-1338, Reynoso-Velasco coll. ( 1♂, 1♀ IEXA) ; [Mpio. Ixtacomitán], Ixtacomitán, Río Blanco, 10-XII-85, col. F. Arias, L. Cervantes y R. Barba / Colección del Instituto de Biología , UNAM, México, D.F. ( 2♂, 2♀ CNIN; 1♂, 2♀ IEXA) ; Mpio. Maravilla Tenejapa, Ixcán, Río Ixcán at Pte. Ixcán , 16°04’33.6’’N, 91°04’12.8’’W, 175 m, 30-Mar-2015, L-1896, Reynoso-Velasco, Sites, Shepard & Barr colls. ( 12♂, 5♀ CNIN; 32♂, 18♀ IEXA) ; Mpio. Maravilla Tenejapa, 13 de Septiembre, Río Puerto Rico at Pte. Puerto Rico , 16°04’47.9’’N, 91°01’17.4’’W, 163 m, 30-Mar-2015, L-1895, Reynoso-Velasco Sites, Shepard & Barr colls. ( 2♂, 2♀ IEXA) ; Mpio. Ocosingo, Ruta Montes Azules, 30-IV-86, F. Arias / Colección del Instituto de Biología , UNAM, México D.F. ( 1♂ CNIN; 1♂ IEXA) ; [Mpio. Ocozocoautla de Espinoza], Arroyo Corzo at km 154 carr. Tuxtla Gutiérrez-Coatzacoalcos , 17°03.189’N, 93°34.03’W, 234m, 25-MAR-2012, J.A. Gómez & R. Novelo colls. ( 3♂, 1♀ IEXA) ; [ Mpio. Palenque ], Palenque, CL 610, 13-XII-73, J. T. Polhemus ( 1♀ USNM) ; Mpio. Pichucalco, El Azufre , Pte. Azufre I, 17°33’25.9’’N, 93°00’28.0’’W, 49 m, 26-Mar-2015, L-1882, Reynoso-Velasco, Sites, Shepard & Barr colls. ( 2♂, 1♀ IEXA) ; Mpio. Pichucalco, Río Pichucalco at Pte. Rosita , 4 km S of Pichucalco ( 800 m S of Río de Janeiro), 17°29’07.2’’N, 93°06’13.5’’W, 44 m, 27-Mar-2015, L1883, Reynoso-Velasco, Sites, Shepard & Barr colls. ( 6♂, 4♀ IEXA) ; Mpio. Solosuchiapa, Solosuchiapa, Río La Sierra , 17º25’40.5’’N, 93º01’35.7’’W, 122 m, 17- May-2012, L-1339, Reynoso-Velasco coll. ( 2♂, 2♀ IEXA; 13♂, 18♀ UMC) ; Mpio. Palenque, Ángel Albino Corzo (1a Sección ), Balneario ( Sin Nombre ), Río Chocolja , 17°17’32’’N, 91°37’49.5’’W, 119 m, 29-Mar-2015, L-1888, Reynoso-Velasco, Sites, Shepard & Barr colls. ( 5♂, 1♀ CNIN; 12♂, 4♀ IEXA) ; Solaya [Solayó]- Río Laja [Lajas], 13-XII-85, F. Arias, L. Cervantes, R. Barba / Colección del Instituto de Biología , UNAM, México, D.F. ( 2♂, 1♀ CNIN; 2♂, 1♀ IEXA) . Morelos: Cuernavaca, 10-V-50 / Colección del Instituto de Biología , UNAM, México D.F. ( 2♀ CNIN; 1♀ IEXA) [in doubt]. Oaxaca: Mpio. Ayotzintepec, San José Mano Marqués, 17º47’26.2’’N, 96º00’15.3’’W, 66 m, 24-May-2012, L-1371, Reynoso-Velasco coll. ( 3♂, 3♀ CNIN; 5♂, 10♀ IEXA; 21♂, 20♀ UMC) ; Mpio. Jalapa de Díaz, Arroyo Espuma , 3 km SW of San Felipe, 18°03’44.2’’N, 96°32’49.2’’W, 152 m, 25-Mar-2015, L-1880, Reynoso-Velasco, Sites, Shepard & Barr colls. ( 4♂, 1♀ IEXA) ; Mpio. Jalapa de Díaz, Sto. Domingo, Río Sto. Domingo , 18°02’15.9’’N, 96°32’57.2’’W, 100 m, L-1881, 25-Mar-2015, L-1881, Reynoso-Velasco, Sites, Shepard & Barr colls. ( 22♂, 13♀ IEXA) ; [Mpio. San José Chiltepec], Río Valle Nal., Peña Rubia, Km 13.1 Rta 175, 100 m, 9-VII-1996, R. Barba & A. Rojas / Colección del Instituto de Biología , UNAM, México D.F. ( 1♂, 1♀ CNIN; 1♀ IEXA) ; Mpio. San Juan Cotzocón, Arroyo Carrizal at km 110 carr. Palomares-Tuxtepec , 17º26’55.6’’N, 95º26’39.1’’W, 94 m, 22-May-2012, L-1365, Reynoso-Velasco coll. ( 2♂, 2♀ IEXA; 4♂, 2♀ UMC) ; Mpio. Santiago Jocotepec, carr. La Alicia-Reforma , ca. 8 km E of Ayotzintepec, 17º40’10.2’’N, 96º04’21’’W, 108 m, 23-May-2012, L-1370, Reynoso-Velasco coll. ( 1♂ UMC) ; Mpio. Santiago Jocotepec, La Alicia , 17º38’57.9’’N, 96º00’38.7’’W, 103 m, 23-May-2012, L-1369, Reynoso-Velasco coll. ( 3♀ UMC) ; Mpio. Santiago Jocotepec, Río Tesechoacán at Centro Ecoturístico Cerro Chango , 17º42’06.6’’N, 95º54’01.6’’W, 54 m, 23-May-2012, L-1367, Reynoso-Velasco coll. ( 3♂, 3♀ IEXA; 2♂, 3♀ UMC) ; Mpio. Santiago Jocotepec, Río Tesechoacán 3.5 km S of San José Río Manso, 17º38’44.3’’N, 95º52’02.1’’W, 61 m, 23-May-2012, L-1368, Reynoso-Velasco coll. ( 4♂, 2♀ UMC) . Veracruz: [Mpio. Catemaco], Catemaco, 23-II-60 / Colección del Instituto de Biología , UNAM, México D.F ( 1♂ IEXA) ; same but 10-VI-64, L. Vázquez / Colección del Instituto de Biología , UNAM, México D.F. ( 1♀ IEXA) ; [Mpio. Catemaco], Catemaco , 10-VI-64 ( 3♀ CNIN; 2♀ USNM) ; same but / Topotype Comp. @ type J. T. Polhemus ‘85 / Ambrysus quadracies Ira La Rivers det. J. T. Polhemus ( 1♀ CNIN) ; [Mpio. Catemaco], Coyame, Lago Catemaco, 4-V-64, B. Ayala / Colección del Instituto de Biología , UNAM, México D.F. ( 1♀ CNIN) ; same but 7-II-1965 B. Ayala / Colección del Instituto de Biología , UNAM, México D.F. ( 3♂, 5♀ UMC) ; Mpio. Santiago Sochiapan, Río Lana at Pte. Río Lana , 17º32’49.8’’N, 95º34’31.6’’W, 53 m, 23-May-2012, L-1366, Reynoso-Velasco coll. ( 2♂, 2♀ IEXA; 2♂ UMC) .

Figures

FIGURE 23. Structures of Ambrysus quadracies La Rivers. (A) Dorsal habitus of male (last abdominal segments removed), (B) sternum VI and subgenital plate of female (terminal abdominal segments removed), (C) 6th and 7th abdominal terga of male, (D) 8th abdominal tergum of male, (E) ventral surface of male phallosoma, (F) genital capsule of male (phallosoma removed).

FIGURE 24. Dorsal habitus, labels, and subgenital plate of female holotype of Ambrysus quadracies La Rivers.

FIGURE 25. Distribution of Ambrysus quadracies La Rivers.