Ambrysus signoreti Stål species complex

Discussion. As given in the treatment of Section 1 of the complex (Reynoso-Velasco & Sites 2022), the most reliable unifying feature among species in the A. signoreti complex is in the ventral surface of the male phallosoma, which includes the presence of small protuberances (pointed or rounded) referred to as “denticles” on the sclerotized and variously shaped endosomal sclerites (e.g., Figs. 1E–1G, 20E). In a few species, the right sclerite is reduced, greatly reduced, or absent; nonetheless, the protuberances are present on the left sclerite, which also can be reduced (e.g., Fig. 35E). Only one species, A. signoreti, lacks both sclerites and in consequence the protuberances; however, molecular evidence clearly supports the inclusion of the species in this complex (Reynoso-Velasco & Sites 2021). Additionally, the great majority of species in this complex, including A. signoreti, exhibit a characteristic maculation, as suggested but not described by La Rivers (1957a). This feature includes extensive light-colored markings (sometimes spotted) at the lateral and posterior margins of the corium (e.g., Fig. 29A). In some species, the marking on the posterior margin extends along the posterolateral angle of the corium (e.g., Fig. 35A).

For convenience, the A. signoreti complex was artificially organized into three sections (Table 1) based on conspicuous characteristics of the female subgenital plate: Section 1 includes females with posterolateral corners extending posteriorly slightly further than the central lobe (Fig. 1H), Section 2 includes those females with the central lobe extending posteriorly further than the posterolateral corners (Fig. 1I), and Section 3, where the females exhibit posterolateral corners and central lobe almost at the same level (Fig. 1J).

Key to the species complexes in the subgenus Ambrysus Stål, the sections in the A. signoreti complex, and the species in its Section 3: female subgenital plate with posterolateral corners and central lobe almost at the same level.

Couplets 1–4: The male phallosoma is open on the apical 1/3 to 1/4 of the ventral surface; referred lobes, when present, are projections of the lateral margins of the apical opening, whereas endosomal sclerites are associated with the endosoma situated inside the phallosoma and visible, sometimes partially, through apical opening. Couplets 5–17: Similar to other species complexes, the shape of the female subgenital plate (SGP) is the most reliable diagnostic feature for species identification; nevertheless, the key secondarily includes characteristics of the males to corroborate the identity of the species, especially for those with similar female SGPs. Also, symmetry of the left and right margins of the SPG is an important feature in the key. For most species/specimens, SGP symmetry/ asymmetry is distinct, but some can exhibit a small degree of asymmetry that is inconspicuous; in such case it was considered negligible and the SGP is reported as symmetrical.

1 – Male phallosoma with a dorsolateral flap on left side (Fig. 1A)............................................................................................ Ambrysus pulchellus complex (refer to Reynoso-Velasco & Sites 2018a)

1’ – Male phallosoma without dorsolateral flap (Figs. 1B–1G)..................................................... 2

2 – Phallosoma with left ventral lobe overlapping right ventral lobe along midline, a pair of endosomal sclerites closely appressed, and lateral margins of phallosoma almost straight (Fig. 1B)... A. pudicus complex (refer to Reynoso-Velasco & Sites 2018b)

2’ – Phallosoma without ventral lobes (Figs. 1D–1G), but if present then not overlapping or touching each other (Fig. 1C); without endosomal sclerites (Fig. 1C), but if present then not contiguous (disconnected) (Figs. 1E–1G) or pointed apices only touching along midline (Fig. 1D); lateral margins of phallosoma sinuous (Figs. 1C–1G)..................................... 3

3 – Phallosoma with left ventral lobe lateroflexed at mid-length, without endosomal sclerites (Fig. 1C)................................................................... A. guttatipennis complex (refer to Reynoso-Velasco & Sites 2016a)

3 – Phallosoma without ventral lobes, with left and right endosomal sclerites (Figs. 1D–1G) or at least left sclerite present (Fig. 35E) (both sclerites absent in A. signoreti; Fig. 29E).......................................................... 4

4 – Phallosoma with endosomal sclerites fang- or claw-shaped and smooth (Fig. 1D)..................................................................................... A. hybridus complex (refer to Reynoso-Velasco & Sites 2016b)

4’ – Phallosoma with endosomal sclerites (right sclerite can be reduced or absent) variously shaped (e.g., rounded, subtriangular, knob-like), with small and rounded or pointed protuberances (denticles) (Figs. 1E–1G, 2E, 4E, 6E, 9E, 12E, 15E, 17E, 20E, 23E, 26E, 35E, 37E)........................................................... A. signoreti complex .......... 5

5 – Female SGP with posterolateral corners extending posteriorly further than the central lobe (Fig. 1A .................................................................................Section 1 (refer to Reynoso-Velasco & Sites 2022)

5’ – Female SGP with central lobe clearly extending posteriorly further than the posterolateral corners (Fig. 1B)......................................................................... Section 2 (refer to Reynoso-Velasco & Sites 2023)

5’’ – Female SGP with posterolateral corners and central lobe almost at the same level (Fig. 1C)............ Section 3 .......... 6

6 – Left margin of female SGP with a large lateral lobe that is truncate (Fig. 26B) or evenly rounded (Fig. 35B); SGP notoriously asymmetrical........................................................................................ 7

6’ – Left margin of female SGP with a small lateral lobe that is rounded (Figs. 2B, 4B, 6B, 9B, 20B, 23B, 29B, 37B) or pointed to right-angled (Figs. 12B, 15B, 17B); SGP asymmetrical (Figs. 4B, 6B, 9B, 23B) or symmetrical (Figs. 2B, 12B, 15B, 17B, 20B, 29B, 37B).......................................................................................... 8

7 – Female SGP with a plate-like and truncate lobe on the left margin; posterolateral corners asymmetrical, left corner lower (Fig. 26B). Scutellum and corium with black-dotted pattern over reddish areas (Fig. 26A)............... A. scalenus La Rivers

7’ – Female SGP with an evenly rounded lobe on the left margin; posterolateral corners symmetrical, at the same level (Fig. 35B). Scutellum and corium without pattern over light-brown to yellowish-brown areas (Fig. 35A)............ A. sitesi Reynoso

8 – Female SGP asymmetrical, lobe on left margin ventrally deflexed (Figs. 4B, 23B, 29B) (bending more evident if specimen in caudal view and slightly tilted upward).................................................................... 9

8’ – Female SGP asymmetrical (Figs. 6B, 9B) or symmetrical (Figs. 2B, 12B, 15B, 17B, 20B, 37B), lobe on left margin not deflexed........................................................................................... 11

9 – Female SGP with posterolateral corners slightly reflexed dorsad (Fig. 4B). Male accessory genitalic process (AGP) evenly curved from base to apex (Fig. 4C).................................................... A. cayo Sites & Shepard

9’ – Female SGP with posterolateral corners not reflexed (Figs. 23B, 29B). Male AGP angled close to base and at distal third (Figs. 23C, 29C)......................................................................................... 10

10 – Female SGP with central lobe as two pointed lobes (Fig. 23B). Male phallosoma rounded apically; endosomal sclerites present (Fig. 23E). Both sexes with posterolateral corners of abdominal segments III and IV strongly produced and spinose (Fig. 23A). Lateral area of pronotum and posterolateral area of corium with profuse dark-brown dotted pattern (Fig. 23A).............................................................................................. A. quadracies La Rivers

10’ – Female SGP with central lobe as two rounded lobes (Fig. 29B). Male phallosoma pointed apically; endosomal sclerites absent (Fig. 29E). Both sexes with posterolateral corners of abdominal segments III and IV barely produced (Fig. 29A). Lateral area of pronotum and posterolateral area of corium without dotted pattern (Fig. 29A)....................... A. signoreti Stål

11 – Female SGP with apical lobes present (Fig. 9B), although sometimes inconspicuous (Figs. 2B, 37B).................. 12

11’ – Female SGP without apical lobes (Figs. 6B, 12B, 15B, 17B, 20B).............................................. 14

12 – Female SGP symmetrical (Figs. 2B, 37B)................................................................. 13

12’ – Female SGP asymmetrical, lateral and pointed apical lobes on right margin slightly less developed (Fig. 9B)................................................................................................ A. dyticus La Rivers

13 – Female SGP with posterolateral corners rounded, central lobe wide (Fig. 37B). Male phallosoma with endosoma not sclerotized apically (Fig. 37E).................................................................... A. sonorensis Usinger

13’ – Female SGP with posterolateral corners pointed, central lobe narrow (Fig. 2B). Male phallosoma with endosoma apically sclerotized on left side, lobe-shaped (Fig. 2E).............................................. A. altiplanus Reynoso

14 – Female SGP with central lobe as two pointed lobes, these lobes and posterolateral corners similar in shape; lateral lobe on right margin inconspicuous (Fig. 6B). Male right pseudoparamere 1.2× as wide as left pseudoparamere (Fig. 6D); phallosoma with right endosomal sclerite rounded and inconspicuous (Fig. 6E). Body length ≤ 9.00 mm.................................................................................................... A. colimanus Polhemus & Polhemus

14’ – Female SGP with central lobe evenly rounded (Fig. 17B) or as two rounded lobes (Figs. 12B, 15B), these lobes and posterolateral corners not similar in shape; lateral lobe on right margin conspicuous (Figs. 12B, 15B, 17B, 20B). Male pseudoparameres subequal in width (Figs. 12D, 15D, 17D, 20D); phallosoma with both endosomal sclerites knob-like (e.g., Fig. 20E). Body length> 10.50 mm ................................................................................... 15

15 – Abdomen with posterolateral corners of segments III–IV slightly produced, acute but not spinose (Figs. 15A, 17A); dorsally with segments III–V usually narrowly exposed. Corium with light areas light-brown to yellowish-brown (Figs. 15A, 17A). Maximum width of pronotum 1.5× length of pronotum and head at midline...................................... 16

15’ – Abdomen with posterolateral corners of segments III–IV produced and clearly spinose (Figs. 12A, 20A); dorsally with segments III–V usually widely exposed. Corium with light areas usually reddish to reddish-brown (Figs. 12A, 20A). Maximum width of pronotum 1.6× length of pronotum and head at midline...................................................... 17

16 – Female SGP with posterior margin about 1/3 of SGP maximum width; central lobe shallowly concave medially, thereby as two low and rounded lobes; apices of lateral lobes at mid-length (Fig. 15B)............................ A. inecol Reynoso

16’ – Female SGP with posterior margin about 2/3 of SGP maximum width; central lobe evenly convex, no medial concavity; apices of lateral lobes clearly posterior to mid-length (Fig. 17B)................................... A. magniceps La Rivers

17 – Female SGP with shallowly concave central lobe slightly beyond level of posterolateral corners, posterior margin between posterolateral corners convex; posterolateral corners usually pointed (Fig. 12B). Male pseudoparameres with posterolateral corners broadly rounded (Fig. 12D); right phallosomal sclerite almost straight, basally directed (Fig. 12E).................................................................................................... A. hydor La Rivers

17’ – Female SGP with shallowly concave central lobe at same level as posterolateral corners, posterior margin almost straight; posterolateral corners usually rounded (Fig. 20B). Male pseudoparameres with posterolateral corners narrowly rounded (Fig. 20D); phallosomal sclerites (at least left one) right-tilted (Fig. 20E).......................... A. occidentalis La Rivers