Ambrysus cayo Sites & Shepard

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 : 12-14

Ambrysus cayo Sites & Shepard

( Figs. 4–5 )

Ambrysus cayo Sites & Shepard 2015 : Ann. Entomol. Soc. Am., 108: 614–617 (original description). Diagnosis. This species can be distinguished from others in this section by the asymmetrical SGP with a ventrally deflexed and rounded lateral lobe on the left margin and a flap-like lateral lobe on the right margin. Additionally, the pointed posterolateral corners are slightly reflexed dorsad and the central lobe is clearly concave medially, giving the appearance of two pointed lobes ( Fig. 4B ). Also, males exhibit a rounded right endosomal sclerite with no denticles and a subtriangular left endosomal sclerite with conspicuous denticles ( Fig. 4E ). Furthermore, males exhibit a uniformly tapering, acuminate, and base-to-apex evenly curved AGP ( Fig. 4C ), which is distinctive within the species complex.

Comparative notes. This is the only species in the complex with posterolateral corners of the SGP reflexed. The shape of the endosomal sclerites of the male phallosoma is similar to that of A. brailovskyi Reynoso & Sites (Section 2) and A. colimanus Polhemus & Polhemus , although the shape and distribution of denticles are different. The shape of the male AGP is comparable to only that of A. convexus Usinger , a member of the A. hybridus Montandon species complex (see Reynoso-Velasco & Sites 2016b).

Discussion. This species measures 9.60–10.88 in length and 6.24–6.88 in width. Sites & Shepard (2015) mentioned a similar condition of the asymmetrical SGP of A. cayo Sites & Shepard to be present in at least six Mexican species, of which, only A. cosmius La Rivers (Section 1), A. quadracies La Rivers , and A. scalenus La Rivers are members of the A. signoreti complex. This resemblance is only superficial as the shape of the male pseudoparameres and condition of the endosomal sclerites suggest a closer relationship with A. colimanus . This morphology-based proposition was supported by recent evidence based on molecular data ( Sites 2022).

Variation. No variation was detected on the diagnostic features.

Type locality. Belize: Cayo District: Privassion Creek 16.6 km N of Augustine, 17º02.899’N, 88º56.910’W .

Repository. Male holotype is housed at the UMC .

Published record: BELIZE: Cayo District ( Sites & Shepard 2015).

Distribution. Ambrysus cayo is distributed in the west-central region of Belize, in the Cayo District ( Fig. 5 ). The localities, all below 600 m, are in the Belize River Basin, in a small area of about 200 km 2 draining the northwestern slopes of the Pine Ridge system. This area is the southernmost section of the Veracruzan biogeographic province. It is likely that the species is at least present in the central-western part of the Petén Department, in northern Guatemala. This area is part of the same river basin and in close vicinity to locations where the species has been collected.

Type material examined. HOLOTYPE ♂ (by original designation). BELIZE: Cayo District: Privassion Creek at road crossing, 16.6 km N of Augustine [= Douglas da Silva], 15-IV- 2014, 486 m, 17º02.899’N, 88º56.910’W, L-1723, R. W. Sites & W.D. Shepard colls., undercuts and marginal vegetation . PARATYPES: same data as holotype ( 1♀ UMC); same but 20-IV-2014, L-1743 ( 1♂, 1♀ UMC); same but 07-I-1995, W.D. Shepard coll., WDS-A-1118 ( 1♂ UMC); Rio On pools at 4.5 km N of Augustine, 16º59.2300’N, 88º58.6240’W, 459 m, 15-IV-2014, [L-1725], R . W. Sites & W.D. Shepard colls., vegetated margins of bedrock pools ( 1♀ UMC); 1.7 km S of Augustine , unnamed stream, 06-I-1996, L-96, R . W. Sites coll. ( 2♂, 1♀ UMC); 5.3 km S of Augustine, unnamed stream, 06-I-1996, W.D. Shepard coll. ( 1♂, 1♀ UMC); 8.4 km N of Augustine , unnamed stream, 17º00.8560’N, 88º58.8180’W, 445 m, 15- IV-2014, L-1724, R . W. Sites & W.D. Shepard colls. ( 1♀ UMC) .

Additional material examined. BELIZE: Cayo District: Mountain Pine Ridge, trib. of Eastern Branch 1.7 mi S of Augustine, 06-I-1996, C.B. Barr coll. ( 2♂, 2♀ EMEC); same but 6 mi S of Augustine, ( 1♀ EMEC); Mountain Pine Ridge , Paddy Creek [ between San Augustine and San Luis], N of San Luis, 31-XII-1973, CL647, J. T. Polhemus coll. ( 1♀ USNM); Mountain Pine Ridge , [ca. 90 meters south of Paddy Creek], N of San Luis, 31-XII-1973, CL648, J. T. Polhemus coll. ( 11♂, 16♀ USNM); Mountain Pine Ridge , N of San Augustine, [ 4 miles south of Privassion Creek], 31-XII-1973, CL650, J. T. Polhemus coll. ( 1♂, 1♀ USNM) .

Figures

FIGURE 4. Structures of Ambrysus cayo Sites & Shepard. (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.

FIGURE 5. Distribution of Ambrysus cayo Sites & Shepard (inset showing detailed distribution in west-central Belize).