Stenaspis Audinet-Serville, 1834

Eya, Bryan K., 2021, Recharacterization of Stenaspis Audinet-Serville, 1834 with a new species from Mexico (Coleoptera: Cerambycidae: Cerambycinae: Trachyderini), Insecta Mundi 2021 (851), pp. 1-36 : 5-13

Stenaspis Audinet-Serville, 1834

Type species: Stenaspis verticalis Audinet-Serville, 1834 (monobasic).

Stenaspis Audinet-Serville 1834: 51 ; Dupont 1838: 50; Castelnau 1840: 419; Blanchard 1845: 145; LeConte 1854: 441; Strauch 1861: 127; Thomson 1861: 211, 1864: 208, 434; Lacordaire 1869: 171; Chenu 1870: 311; Gemminger and von Harold 1872: 2967; LeConte 1873a: 314; Bates 1880: 76; LeConte and Horn 1883: 299; Leng 1886: 60; Casey 1912: 318; Aurivillius 1912: 458; Bradley 1930: 241; Zajciw 1960: 144, 1961: 401; Arnett 1962: 863, 881; Linsley 1962: 98; Monné 1994: 34; Monné 2005: 642; Monné 2012: 62; Eya 2015: 361.

Smileceras LeConte 1850: 8 ; Thomson 1861: 380, 1864: 208, 434.

Redescription. Form, robust, parallel-sided to slightly tapered posteriorly, dorsum sparsely pubescent. Head with frons square, perpendicular, abruptly separated from anteocular space, impressed transversely above clypeus with deep pit on each side of transverse impression, median line canaliculate, extending to vertex between eyes, vertex and frons rugulose, irregularly punctate ( Fig. 1–6); mandible arcuate, striate-punctate, outer edge excavate, apices simple; palpi short, subequal, last segment not expanded, outer edge impressed, apex truncate; gena quadrate, lower lobe of eye well separated from base of mandible ( Fig. 1, 4); antennal tubercles prominent; eyes moderately large, finely faceted, upper lobes small, well separated; antennae elongate, 11-segmented, scape conical (without excavated or impressed area in basal half), apices of antennomere 3–7 darker, slightly enlarged and expanded, 11 th antennomere appendiculate. Pronotum broader than long, narrower than base of elytra at humeri, sides rounded, angulate or tuberculate; anterior angles inflated, broadly rounded or with obtuse callus; prosternum with intercoxal process narrower than coxal cavity, apex protuberant, ridged between coxae, subvertical, abruptly declivous behind ( Fig. 7a–9a), coxal cavities wide open behind; mesosternal intercoxal process not protuberant, about level with top of coxae ( Fig. 7b–9b) and abruptly declivous and concave in front. Scutellum triangular, elongate toward apex, acutely pointed, glabrous. Elytra with apices unarmed, rounded to suture ( Fig. 10–12). Legs slender, hind femora linear, compressed, not attaining apex of elytra; hind tarsi with tarsomeres triangular, explanate, first tarsomere shorter than following two together, third tarsomere cleft to base.

Discussion. According to Audinet-Serville (1834: 52), Stenaspis is a genus with a thorax that is laterally dilated, almost transverse, square (especially in males), tuberculate on each side at the middle, and obliquely tapered from the tubercle to the posterior angle. The pronotal disc is glabrate with sides irregularly punctate. The scutellum is large, elongate triangular, and narrowly acute at the apex. The antennae are glabrous, longer than the body in males and is described as having 12 articles with the second segment short, globular, and segments 3–8 cylindrical, and the following segments flattened, elongate and the terminal segment longest.

The antennae of four species of Stenaspis (i.e., S. castaneipennis , S. solitaria , S. superba and S. verticalis ) examined are 11-segmented with the last antennomere appendiculate as described later by Linsley (1962: 98). The intercoxal process of the prosternum is cuneiform, compressed and protruding ( Fig. 7a, 8a, 9a). The mandibles are short and thick. The elytra are almost parallel-sided, slightly narrowed apically, the humeral angles are rounded, and the apices are rounded and unarmed. The legs are medium length, the femora are clubbed and elongate. The body of Stenaspsis is glabrate and more or less shining.

The prothorax of Stenaspis is sexually dimorphic as in Crioprosopus and Callistochroma . Linsley (1962: 98–99) described the two males of North American Stenaspis (i.e., S. verticalis and S. solitaria ) as having the dorsal surface of the pronotum coarsely, irregularly punctate, the lateral surface finely, densely punctate, and the prosternum with transverse subrectangular impressed areas on each side of the middle that are finely and densely punctate. Furthermore, he stated that females of both species have the pronotum coarsely, irregularly punctate on the lateral surface, and the prosternum coarsely punctate and transversely rugose. The sides of the male pronotum (or the prosternal episternum or proepisternum) are finely, densely punctate and inflated ( Fig. 15, 16a), and this finely punctate area is clearly demarcated from the coarsely punctate dorsum of the disc ( Fig. 16b), and is vaguely divided from the subrectangular impressed area of the prosternum ( Fig. 17a–b). There is considerable variation in the shape of the male pronotum in S. verticalis and S. castaneipennis ( Fig. 15, 18, 24, 27). Some individuals have rounded sides due to well developed and inflated anterior angles (or proepisternum, Fig. 15–16, 24–25), which merges over the lateral tubercles behind middle, whereas other males with less developed anterior angles have more prominent lateral tubercles ( Fig. 18, 27). Based on the specimens examined, the male S. solitaria all have well developed lateral tubercles ( Fig. 33a) with rounded anterior angles ( Fig. 33b), which do not extend and merge over the lateral tubercles. In the females, the coarse punctures on the side of the pronotum merge with punctures on the dorsum and are not clearly demarcated as in the males ( Fig. 22, 31). The anterior angles of the pronotum in females are obtusely callused and obliquely tapered toward the apex ( Fig. 21a, 30a). Females of all four species (i.e., S. castaneipennis , S. solitaria , S. superba and S. verticalis ) have prominent lateral tubercles behind the middle and anterior angles broadly callused, and proepisternum and prosternum coarsely punctate. As in other trachyderine genera there are five discal calli on the pronotum, two antemedial, one on each side of the middle, and three postmedial near the base, one in the middle and one each on either side ( Fig. 15, 33). These five discal calli in Stenaspis are vaguely protuberant, and the spaces in the middle between these calli are usually flattened. In some specimens; however, the three calli near the base, especially the one in the middle, are more visible than the two in the anterior half. Stenaspis superba is the only species with the two anterior dorsal calli more prominent ( Fig. 39) and the pronotal disc convex instead of flattened ( Fig. 40).

The prosternal intercoxal process of S. castaneipennis , S. solitaria and S. verticalis is also variable in shape ranging from uniformly sloping to the apex and abruptly declivous or concave behind ( Fig. 42–43) to concave and abruptly acuminate at the apex ( Fig. 44–47). Variation in the shape of prosternal process is more evident in S. verticalis , as compared to S. castaneipennis where the prosternal process is more commonly concave and abruptly acuminate at the apex. In S. solitaria the prosternal process is usually more uniformly sloped to the apex.

The scape in S. castaneipennis , S. solitaria , S. superba and S. verticalis is conical (without excavated area in basal half), usually glabrate and sparsely punctate or coarsely, separately punctate ( Fig. 51–53; 57–61). The antennae of S. verticalis and S. castaneipennis are bicolored and antennomeres III–V are glabrous and sparsely punctate except apically darker and more densely punctate and pubescent ( Fig. 57–58). In S. solitaria , which is concolorous (usually all black or reddish-brown) the antennomeres III–V are more densely, uniformly punctate throughout except for the basal half of the third antennomere, which is less densely punctate ( Fig. 60). In the holotype female of S. superba the antennomeres are black to dark brown with scape to the fourth antennomere sparsely punctate, and densely, finely punctate from antennomere V to XI ( Fig. 61).

Other commonalities between these four species of Stenaspis include the elongate triangular scutellum which is narrowly acute at the apex (i.e., length ≥ width) and the elytra which are distinctly margined laterally and the apices unarmed as in Crioprosopus . The lateral margination of each elytron usually ends just prior to reaching the apex, and the elytra are obliquely truncate or rounded apically.

Herein, the genus Stenaspis is characterized as follows: (1) head with frons large, square, perpendicular, abruptly separated from anteocular space ( Fig. 1–6); (2) dorsum of scape without excavated or impressed area in basal half ( Fig. 51–53); (3) prosternal intercoxal process protuberant and ridged between coxae and subvertical to vertical or concave behind ( Fig. 7–9); (4) mesosternal intercoxal process not protuberant, about level with top of coxae and abruptly declivous in front ( Fig. 7–9); (5) pronotum narrower than base of elytra at humeri with sides rounded, angulate or frequently tuberculate slightly behind middle, and anterior angles rounded or broadly callused ( Fig. 15–21, 24–30, 33, 36, 41); (6) the area between the five discal calli on the pronotum almost flat, usually glabrate, and dorsal calli usually absent or vague (e.g., Fig. 15–16, 21–22, 24, 30–31, 33–34, 36–37); (7) hind tarsi with tarsomeres triangular, explanate, first tarsomere slightly shorter than following two together ( Fig. 62–65); (8) males with proepisternum and prosternum finely, densely punctate, and proepisternum inflated and clearly demarcated from the coarsely punctate pronotal disc ( Fig. 16, 19, 25, 28, 34), and prosternum with densely punctate transverse subrectangular area on each side of middle ( Fig. 17a, 20, 26, 29a, 35a); (9) females with sides of pronotum laterally tuberculate behind middle ( Fig. 21, 30, 36, 39) and coarsely punctate with punctures merging with coarse dorsal punctures ( Fig. 22, 31, 37, 40), proepisternum not clearly demarcated from the pronotal disc as found in males, and anterior angles frequently broadly or obtusely callused ( Fig. 21a, 30a, 36a, 41); and (10) elytra distinctly margined laterally, and apices of elytra unarmed and truncate or rounded at sutural angle ( Fig. 10–12).

Crioprosopus and Callistochroma can be differentiated from Stenaspis by the prosternal intercoxal process that is arcuate at the apex ( Fig. 48–50), dorsum of scape with basal half excavate ( Fig. 54–56), tarsomeres of hind

62 63 64 65 66 67 68 tarsi narrow and elongate, and first tarsomere subequal to the following two tarsomeres together ( Fig. 66–68). Frequently, the last tarsomere with the claw (e.g., Crioprosopus amoenus Jordan, Crioprosopus chiriquiensis Eya and Crioprosopus servillei Audinet-Serville ) is much more elongated than in Stenaspis . The prosternal intercoxal process of Stenaspis is protuberant or ridged behind the coxae and vertical or concave behind ( Fig. 42–47), the scape is without a dorsal excavation ( Fig. 51–53), and the hind tarsomeres are triangular and explanate with the first tarsomere slightly shorter than tarsomeres two and three together ( Fig. 62–65). In general, the integument of Crioprosopus and Callistochroma is more glabrous and the punctures are finer than in Stenaspis . Also, the dorsum of antennomeres III–V is frequently canaliculate or impressed in many species of Crioprosopus (i.e., C. amoenus , C. chiriquiensis and C. servillei , and in males of Crioprosopus thoracicus (White) (i.e., Crioprosopus basileus Bates ), Crioprosopus championi Bates , Crioprosopus gaumeri Bates , Crioprosopus hondurensis Eya , Crioprosopus iridescens White , Crioprosopus nieti Chevrolat , Crioprosopus rimosus (Buquet) and Crioprosopus wappesi Eya ) ( Fig. 158–160), while such sculpturing of antennomeres III–V is not found in Stenaspis .

Etymology of the name Stenaspis is Greek: στενὸς, narrow and άσπίς, shield referring to the elongated scutellum as described by Audinet-Serville (1834: 51) and Tavakilian (2020).

Key to Group III-Stenapses with Abruptly Separated Anteocular Space (partially adapted from Linsley 1962: 91 and modified from Eya 2015: 360)

1. Elytra distinctly margined at sides ( Fig. 69–74)................................................ 2

– Elytra obtusely margined at sides ( Fig. 75–77)................................................. 6

2(1). Dorsal surface of head, pronotum and elytra densely, coarsely, contiguously punctate (e.g., Fig. 13–14)... 3

– Dorsum glabrate, if pronotum or head densely punctate then elytra glabrous or rugulose, punctures fine and well separated..................................................................... 4

3(2). Elytral disc, femora, tibiae and ventral surface covered with long, erect, pale hairs, dorsal surface shining; ventral surface of femora and tibia densely, deeply punctate; lateral spine on pronotum obtuse; lateral margin of pronotum and elytra narrowly reddish; 12–24 mm ( Fig. 13–14)....... Pilostenaspis Eya

– Elytra without long erect hairs (or with very short hairs obscurely covering surface); femora and tibiae finely punctate, not covered with long, erect hairs, elytra black with broad yellowish or reddish bands or maculae, lateral spine on pronotum prominent, acute, recurved; 26–36 mm ............................................................................. Megapurpuricenus Eya

4(2). Basal half of scape excavate or scarred; prosternum with intercoxal process arcuate at apex; tarsomeres of hind tarsi elongate, narrow, 1 st tarsomere subequal in length to following two together ( Fig. 54–56, 48–50; 66–68)......................................................................... 5

– Basal half of scape not excavate; prosternum with intercoxal process protuberant or ridged between coxae, vertical or concave behind; mesosternum not protuberant, about level with top of coxae; tarsomeres of hind tarsi short, explanate, 1 st tarsomere shorter than following two together ( Fig. 51–53, 42–47, 62–65).................................................. Stenaspis Audinet-Serville

5(4). Mesosternal intercoxal process obtusely tuberculate and extending well below the plane of prosternal intercoxal process ( Fig. 50b); prothoracic sculpture of male usually confined to limited area towards anterior angle of disc ( Fig. 56); apices of elytra obliquely angulate, with outer armature, sutural angle rounded or acute; antennae with dorsal surfaces of antennomeres III–IV flattened but not canaliculate; abdominal segments usually glabrous............................... Callistochroma Eya

– Mesosternal intercoxal process without obvious projections or subtuberculiform ( Fig. 48b, 49b); prothoracic sculpture of male with disc finely, densely punctate throughout ( Fig. 158–160); apices of elytra rounded or subtruncate, with or without outer armature; antennae with dorsal surfaces of antennomeres III–V frequently canaliculate from apical 2/3 of III; abdominal segments usually densely clothed with silken pubescence............................... Crioprosopus Audinet-Serville

6(1). Pronotum armed with a lateral spine......................................................... 7

– Pronotum subcylindrical or rounded, without lateral spine; elytra with a pair of transverse yellowish bands; antennal tubercles prominent, vertex distinctly concave; body finely pubescent.................................................................... Aethecerinus Fall and Cockerell

7(6). Body glabrate, dorsum opaque, elytra coarsely punctate at base................ Purpuricenus Dejean

– Body pubescent, elytra sulcate or with distinct threadlike costae......... Tragidion Audinet-Serville