Ischnocnemis sexualis Bates 1885
Creators: name: Eya, Bryan K.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Cerambycidae
Ischnocnemis
Ischnocnemis sexualis

description: Ischnocnemis sexualis Bates, 1885
(Fig. 359–381)
Ischnocnemis sexualis Bates 1885: 328; Aurivillius 1912: 473 (cat.); Blackwelder 1946: 590 (cat.); Chemsak et al. 1992: 83 (cat.); Chemsak and Noguera 1993: 63 (dist.); Monné 1994: 64 (cat.); Monné and Giesbert 1994: 146 (cat.); Noguera and Chemsak 1996: 402 (dist.); Swift et al. 2010: 32 (dist.); MacRae et al. 2012: 180 (biol.)
Ischocnemis sexualis Linsley 1935: 100 (dist., genus name misspelled)
Redescription. Male: Length 10–12 mm. Form small, elongate, narrow, slightly tapered apically; integument entirely black (Fig. 359), pronotum occasionally reddish with anterior and posterior margins and prosternum black (Fig. 363), elytra all black (Fig. 359–366, 376–377) or black with vague bluish-violet cast (Fig. 367, 378, 380). Head small; vertex, finely, confluently punctate; front finely, irregularly punctate (Fig. 369–371); postclypeus glabrate to irregularly punctate, distal margin finely punctate; antennal tubercles moderately prominent with apices angulate; genae with lower half triangular, finely, irregularly punctate (Fig. 370); pubescence on margins of postclypeus, antennal tubercles, and dorsal anterior margin of genae obscure, short and erect, setae along margins of upper eyes, sparse, long and erect; labrum minutely, densely punctate, pubescence moderately densely and suberect; antennae slender, exceeding elytral apices by three antennomers; scape conical densely, deeply, contiguously punctate, pubescence obscure, very short, depressed; antennomeres II–VI cylindrical with apices slightly enlarged, integument finely, densely punctate, obscurely pubescent with short depressed setae, remaining antennomeres opaque, densely, minutely punctate and densely covered with minute, appressed setae with few short depressed setae on apices; antennomeres from V carinate on inside surface; antennomere III longer than I; IV shorter than III, longer than I; V longer than IV, subequal to III; VI, VII, VIII, and IX subequal to V; X slightly shorter than IX; XI longest vaguely appendiculate on apical third. Pronotum as long as wide (L/W: 0.97–1.06), cylindrical, sides slightly rounded; disc shallowly convex, opaque, basal half with three vaguely visible sparsely punctate calli, a longitudinally elongate one in middle and one each on either side near base; apical margin collared, narrowly constricted behind; basal margin vaguely impressed on sides (Fig. 372–374); punctures dense and contiguous; pubescence absent; proepisternal area more sparsely, irregular punctate than pronotal disc, pubescence sparse, obscure, minute, erect; prosternum barely impressed, apical half transversely plicate, basal half confluently punctate, area above coxae on each sides rugulose, pubescence short, suberect; mesosternum densely, coarsely punctate, pubescence short, obscure, suberect, mesosternal intercoxal process as wide as coxal cavity; mesepisterna and mesepimera with punctures fine, dense, contiguous, obscurely clothed with appressed, pale pubescence; metasternum with integument nitid, coarsely, densely, discretely punctate, sparsely clothed with depressed setae, punctures sparser on either sides of midline; metepisterna finely, contiguously punctate, obscurely clothed with appressed, pale pubescence. Scutellum black, triangular, irregularly punctate. Elytra 2.9 times as long as broad; each elytron with raised subsutural and vague submarginal glabrous costae and another faint costa frequently visible in middle (Fig. 380–381), integument between costae densely, discretely punctate, pubescence absent or sparse, very short and suberect; apices either serrate-truncate (Fig. 376), sinuate-truncate (Fig. 377), or truncate (Fig. 378), exterior angle unarmed. Legs slender, nitid; femora finely, densely punctate, obscurely clothed with minute, depressed setae on dorsum and sides, setae longer on ventral surface; pro- and mesofemora slightly clavate; metafemora linear, slightly arcuate near base, shorter than body and attaining fourth abdominal sternite; tibiae densely punctate, clothed with short, depressed setae; protibiae with inner surface densely clothed with short depressed, pale pubescence; metatarsomere I subequal to tarsomeres II and III combined (Fig. 379). Abdomen nitid, very finely, discretely punctate, pubescence obscure, sparse, short, and appressed, punctures sparser in middle, finer and denser on sides; last sternite with apex truncate, and vaguely emarginate at middle.
Female: Length 9–14 mm. Form slightly more robust and parallel-sides than male. Integument black as in male, pronotum and proepisternal area usually reddish with anterior and posterior margins and prosternum black (Fig. 361, 365) or pronotum all black with reddish cast. Prosternum with apical half transversely plicate as in male, basal half transversely, contiguously punctate. Antennae attaining apex of elytra or longer than body by an antennomere. Abdomen with apex of last sternite broadly truncate.
Materials examined. MEXICO: Jalisco: 25.1 km S La Huerta, Hwy 80, 15 Oct. 1995, B.K. Eya (5 males, 6 females, BKEC); Estación de Biología Chamela, 23 Oct. 1995, B.K. Eya (1 female, BKEC); 14/ 23 Oct. 1986, J.A. Chemsak (1 male, 1 female, BKEC). Morelos: Cuernavaca, Nov. 1902, Koebele Col. (1 male, CASC); Morelos, Koebele Col. (1 male, CASC); Cañón Lobos near Cuernavaca, 17/ 18 Oct. 1984, F. Hovore (1 male, 1 female, CASC). Oaxaca: 1 km N Jct. Hwy 200/ S.P. Huamelula, 19 Oct. 2005, B.K. Eya (3 males, 2 females, BKEC). Guerrero: Iguala, Sept., Barrett, A. Fenyes Col. (1 female, EMEC); 25 km W Iguala, 19 Oct. 1984, F. Hovore (6 males, 1 female, CASC); 33 km W Iguala, 27 Sept. 1994, J.A. Chemsak (2 males, 1 female, EMEC); Mochitlán, 24 Sept. 1964, E.G Linsley, A.E. Michelbacher (1 male, EMEC); 6 km W Tixtla, 15 Oct. 1984, F. Hovore (1 female, CASC); 6 km W Tixtla, 20 Oct. 1984, F. Hovore (3 males, 2 females, CASC).
Discussion. Bates (1885: 328) describes this species as similar and close to Mannophorus ferreus Bates (i.e., female of M. laetus LeConte) but narrower and sublinear in form. The elytra are metallic steel blue black, subnitid, closely punctured with two narrow shiny costae on each side, and apices truncate. The thorax is narrow, oblong, slightly rotundate, and closely but not as coarsely, confluently punctate (as in M. ferreus). The scutellum is wide and triangular. The antennae of males are longer than elytra. Length: 5 lines (i.e., 10.6 mm), male. Habitat reported by Bates is Mexico.
According to Bates (1885: 328), this species was “named as Leptocnemus sexualis, Chevrolat, in Salle collection;” however, noted that this “choice of name was enigmatic” because the female was not “represented in the same collection.” He notes that Chevrolat may have been referring to M. ferreus as the probable female, in which case the name sexualis “would be applicable,” although “the differences between the two species in form and sculpture” are remarkably different.
Ischnocnemis sexualis Bates can be distinguished from the other species by all black integument, and a prominent subsutural costa on each elytron (Fig. 380). The pronotum is opaque and densely contiguously punctate. Bates refers to this species as having two narrow shiny costae on each side of elytra, which is describing the prominent subsutural, and longitudinal costae between the subsutural and submarginal ones visible on the dorsum of each elytron (Fig. 380–381). The submarginal costae on the sides are often vaguely visible in this species. The elytra are more prominently costate in specimens from Jalisco and Guerrero than those from Oaxaca. The pubescence on dorsum is nearly obsolete or very short as in I. glabra and I. caerulescens. Specimens from Guerrero have dark metallic blue-black elytra (Fig. 367, 378, 380) with very short, suberect setae, more distinct calli on basal half of pronotal disc (Fig. 374), and sternum that are more densely clothed with longer, erect setae. Individuals from Jalisco and Oaxaca have black, nitid elytra devoid of pubescence (Fig. 376–377), pronotum with dorsal calli nearly absent, and sternum with pubescence very short and sparse or almost obsolete. Females from Jalisco and Oaxaca have reddish pronotum, while the disc of a females from Guerrero are all black with reddish cast.
description: Published as part of Eya, Bryan K., 2024, Revision of trachyderines related to Sphaenothecus from North America with description of three new genera, and new species of Lophalia Casey, 1912, Mannophorus LeConte, 1854, and Ischnocnemis Thomson, 1864 (Coleoptera: Cerambycidae: Cerambycinae: Trachyderini), pp. 1-94 in Insecta Mundi 2024 (61) on pages 68-70, DOI: 10.5281/zenodo.14662132