Stigmella bipartita Diškus & Stonis, 2016

Stonis, Jonas R., Diškus, Arūnas, Remeikis, Andrius, Davis, Donald R., Solis, M. Alma & Torres, Nixon Cumbicus, 2016, The first record of Baccharis L. (Asteraceae) as a host-plant genus for Nepticulidae (Lepidoptera), with description of new Stigmella species from South America, Zootaxa 4136 (1), pp. 101-128 : 107-110

2. Stigmella bipartita Diškus & Stonis , sp. nov.

( Figs. 3 , 20–32 )

Type material. Holotype: ♂, ECUADOR: Pichincha Province, 11 km NW Alóag, 0°26'12"S, 78°37'19"W, elevation 3165 m, mining larvae on Baccharis emarginata (Ruiz & Pav.) Pers. 18.xi.2007, field card no. 4930, leg. A. Diškus, genitalia slide no. AD 604♂ ( ZMUC). Paratype: 1 ♂, same label data as holotype, genitalia slide no. AD 626♂ ( ZMUC).

Diagnosis. Externally, adults of the new species resemble the Andean S. emarginatae sp. nov. from which they differ in the grey-brown forewing and in absence of the apical fascia. In the male genitalia, the new species differs from all other known Neotropical Stigmella in the combination of two very large cornuti, a short ventral plate of vinculum without sublateral lobes, a rounded transtilla, and a stout gnathos.

Male ( Figs 25–27 ). Forewing length about 2.2–2.5 mm; wingspan about 4.9–5.5 mm (n=2) Head: palpi cream; frontal tuft brownish orange; collar pale brown to brown with golden gloss; scape golden cream; antenna half the length of forewing or slightly longer; flagellum with 32 segments, dark grey-brown to fuscous, with purple iridescence. Thorax and tegula dark grey-brown with golden gloss. Forewing brown-grey, glossy; fascia distinctly postmedian, whitish with some silvery gloss; apex of forewing slightly darker, with very weak purple irridescence (or dark brown at certain angle of view); terminal and tornal cilia grey-brown; underside of forewing dark brown, with no spots or androconia. Hindwing grey-brown on upper side and underside, with no androconia; its cilia greybrown. Legs pale grey-brown, laterally dark brown or fuscous with weak purple iridescence. Abdomen fuscous with metalic shine on upper side, grey-cream on underside; anal tufts very short, pale grey; anal plates cream.

Female. Unknown.

Male genitalia ( Figs 28–32 ). Capsule only slightly longer (205–250 µm) than wide (225–230 µm). Vinculum without lateral (anterior) lobes; ventral plate of vinculum short (60 µm). Uncus 60–75 µm broad, with two lobes, each bearing two large papillae ( Fig. 28 ). Gnathos stout, 75–90 µm long, with two caudal processes broading basally ( Fig. 28 ); central plate of gnathos large, 85–90 µm broad, trapezoidal. Valva ( Figs 29, 32 ) 195–200 µm long, 75–80 µm broad, with two pointed apical processes; inner lobe almost straight or slightly bulged; transtilla with broadly rounded (lobe-like) sublateral processes ( Fig. 28 ). Juxta membranous (hardly visible), triangularlyshaped, broadening caudally. Phallus ( Figs 30, 31 ) 205–210 µm long, 90–100 µm broad; vesica with two very large (105–115 µm long) cornuti ( Fig. 30 ); no small spine-like cornuti developed. The ratio of cornuti and phallus tube is about 1:2.

Bionomics. Larvae mine in leaves ( Fig. 23 ). Host-plant: Baccharis emarginata (Ruiz & Pav.) Pers. (Asteraceae) ( Fig. 21 ). Larvae mine in late November and early December. Contorted or sinuous gallery of mine with central line of dark brown to black frass ( Fig. 23 ). Larval exit slit on upper side of the leaf. Cocoon beige ( Fig. 24 ); length 2.1–2.5 mm, maximal width 1.3–1.5 mm. Adults emerged in December.

Distribution ( Fig. 3 ). This species occurs on the western slopes of the equatorial Andes ( Ecuador), at altitudes about 3000–3200 m ( Figs 20, 22 ).

Etymology. The species name is derived from the Latin bipartitus (divided in two parts; double) in reference to the unusual set of two very large cornuti of the male genitalia.

Figures

FIGURE 3. Current records of Stigmella species feeding on plants from the genus Baccharis L.

FIGURES 20 – 27. Stigmella bipartita Diškus & Stonis, sp. nov. 20, 22, habitat, NW of Alóag, Pichincha Province, Ecuador, the equatorial Andes, elevation 3165 m; 21, host-plant Baccharis emarginata (Ruiz & Pav.) Pers.; 23, leaf-mine; 24, cocoon; 25, male adult, holotype; 26, same, left forewing; 27, same, right forewing.

FIGURES 28 – 32. Male genitalia of Stigmella bipartita Diškus & Stonis, sp. nov. (ZMUC). 28, capsule with phallus, holotype, genitalia slide no. AD 604; 29, valvae, holotype, genitalia slide no. AD 604; 30, phallus, holotype, genitalia slide no. AD 604; 3 1, same, paratype, genitalia slide no. AD 626; 32, capsule without phallus, paratype, genitalia slide no. AD 626.