Macrostemum hyalinum

Macrostemum hyalinum (Pictet 1836)

(Figs. 1–2)

Hydropsyche hyalina Pictet 1836, 402, Plate [Type locality: “Indes Orientales”; type depository unknown; sex unknown]; Macronema hyalinum (Pictet) — Burmeister 1839, 916 [Type locality; distribution];

Ulmer 1905b, 67, 68, 69, Plate 2 [wings; ♂; distribution];

Ulmer 1907, 75, 76, Plate 3 [♂; wings];

Ulmer 1957, 339 [type species of genus Macrostemum, a synonym of Macronema];

Fischer 1963, 188 [distribution];

Flint 1978, 389, 413, 416 [distribution, ♂, wings];

Macrostemum hyalinum (Pictet) — Flint & Bueno-Soria 1982, 367–369 [resurrected Macrostemum from synonymy];

Flint 1996, 412 [distribution];

Flint et al. 1999, 68 [taxonomic notes; distribution];

Marinoni & Almeida 2000, 286 [distribution];

Paprocki et al. 2004, 8 [distribution];

Hollier 2007, 53 [holotype situation];

Dumas et al. 2009, 358 [distribution];

Calor 2011, 321 [distribution];

Nogueira & Cabette 2011, 351 [distribution];

França et al. 2013, 319, 320, 321, 322, 323, Plates 10, 11 [description; ♂; wings; type locality; distribution; taxonomic notes]; Paprocki & França 2014, 30 [distribution];

Holzenthal & Calor 2017 [taxonomic notes, distribution].

According to the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 1999), the neotype of a nominal species-group taxon may be designated under specific conditions: a) agreeing with Articles 75.1 and Recommendation 75A, M. hyalinum does not have holotype, lectotype, syntype, prior neotype, paratypes, or paralectotypes (Hollier 2007); b) because of the potential confusion concerning the correct application of the name Macrostemum hyalinum, this neotype designation is not a matter of curatorial routine (Art. 75.2); c) this designation satisfies the qualifying conditions of Article 75.3—the neotype is designated expressly to help clarify the taxonomic status of at least two potential synonyms and the type locality of M. hyalinum needs clarification [Art. 75.3.1. Pictet (1836) wrongly cited the type locality.]. The diagnostic characters for the species are provided below (Art. 75.3.2). The collection data and description are unique for the specimen designated (Art. 75.3.3). The reasons we believe the type series for M. hyalinum is lost were provided by Hollier (2007; Art. 75.3.4). The structure of the proposed neotype is consistent with Pictet’s (1836) description (Art. 75.3.5). The neotype specimen is from Espírito Santo (Brazil), the first locality mentioned for this species after its description (Ulmer 1905b; Art. 75.3.6). The neotype specimen is the property of the Coleção Zoológica Norte Capixaba (CZNC), Universidade Federal do Espírito Santo (UFES; Art. 75.3.7).

Macrostemum hyalinum can be diagnosed by the two transverse rows of setae near mid-length of abdominal segment X. Abdominal segment X is subtriangular and apically rounded (lateral view). The phallotremal sclerite resembles that of M. digramma but does not have a pair of dorsal processes. Forewings are dark, with hyaline marks, each with three distinct spots beginning near the middle of the posterior margin and extending toward the apical area (Fig. 2A).

Description. Adult in ethanol. Forewing length 8.5 mm (n = 1). Head dark brown with small medial carina and warts. Compound eyes brownish. Scape brownish with ferruginous and golden setae. Maxillary palps brownish yellow and covered by ferruginous and golden setae. Pro-, meso-, and metathoraces dark brown. Legs brownish yellow. Tibial spur formula 2,4,4. Forewings dark and hyaline, each with three distinct spots beginning near middle of posterior margin and extending toward apical area. Discoidal cell present. Radial sector markedly expanded (Fig. 1).

Male genitalia. Abdominal segment IX with medial acuminate keel dorsally and setae covering right and left sides (dorsal view) (Fig. 2E); anterior margins sinuous; posterior margins sinuous, covered by setae, and each side with one deep notch (lateral view) (Fig. 2B). Segment X bilobed with wart on rounded apex of each lobe (dorsal view) (Fig. 2E); subtriangular and apically rounded, with two transverse rows of setae near nid-length (lateral view) (Fig. 2B). Inferior appendages almost uniformly wide, covered by small setae throughout their length and longer setae on dorsal surfaces; each with basal segment two to three times length of apical segment. Phallus arched; apex subtruncate (lateral view) (Fig. 2C); phallotremal sclerite without dorsal process; anterior margin concave and posterior margin bearing pair of large rounded prominences (ventral view) (Fig. 2D); phallotrema rounded, concave, apically positioned on posterior surface of phallus (Fig. 2C).

NEOTYPE. BRAZIL: Espírito Santo: Domingos Martins, Cachoeira I, 20°14’48.3”S, 40°43’31.2”W, 650 m, Coleta Ativa, MZUSP (Museu de Zoologia da Universidade de São Paulo) leg., 1 male (alcohol; MZUSP). [label paper is red and text is printed].

Remarks. This species is variable in the color pattern of the wings and male genitalia (França et al. 2013). The apical spots of the forewing can extend to the edge and segment X, in lateral view, can be ovoid to subtriangular, apically rounded or acuminate. Macrostemum brasiliense also has variations in the wing color pattern and male genitalia, demonstrating intraspecific variation in the genus. Macrostemum hyalinum, Macrostemum ulmeri, and Macrostemum felker differ morphologically only by wing characteristics.

The structures of the male genitalia, such as segments IX and X, inferior appendages, and phallus are similar in species of this genus. We recommend observing the phallotremal sclerite in each species, since it is a morphological structure of great importance in determining Macrostemum species.

Distribution. Brazil (ES).