Stigmella nigriverticella (Chambers, 1875)

(Figs 1, 7–12, 30, 32–34, 46–54)

Material examined. 6♂, 14♀, Guatemala, Quetzaltenango, 14°47'27"N, 91°32'09"W, mining larvae on Quercus spp., 2500 m, 08.ii.2012, field card no. 5120, LT-GT Scientific Expedition, genitalia slides nos RA483, RA484, RA485, RA486, RA487, RA488, RA490 (ZMUC); 2♂, Panajachel, 14°45'06''N, 91°09'43''W, elevation ca. 1657 m, montane forest, larva on Quercus spp., 22.ii.2012, ex pupa iii.2012, LT-GT Scientific Expedition, genitalia slides nos AD516, AD514 (from pupa) (ZMUC).

Diagnosis. The male genitalia differ from Stigmella castaneaefoliella (Chambers 1875) and S. flavipedella (Braun 1914) by the absence of cornuti. From all other species of the saginella group, it differs by the combination of elaborated gnathos, narrow uncus, relatively slender valva and X-shaped juxta.

Male (Figs 32–34). Forewing length 2.2–3.0 mm; wingspan 4.8–6.4 mm. Head: palpi cream to yellowish cream; frontal tuft always black on vertex, sometimes yellowish cream in frontal part; collar and scape yellowish cream, occasionally greyish cream; antenna with 27–30 segments, slightly longer than half of forewing; flagellum grey-brown or blackish on upper side, grey-cream to grey on underside. Thorax yellowish cream; tegulae black in front. Forewings yellow-cream with black markings (the pattern may considerably vary; see figs 32, 33); cilia grey to fuscous (on tornus) to cream (on apex); underside of forewing usually blackish, sometime grey-cream to dark grey, but always with elongated yellow-cream spot on forewing apex (Fig. 34). Hindwings and cilia of hindwings vary from usually grey to dark grey. Legs dark grey or black on upper side, yellowish cream on underside. Abdomen black to dark grey on upper side, yellow-cream on underside; anal tufts cream to pale grey.

Female. Antenna with ca. 26–28 segments. Abdomen vary from yellow-cream to blackish grey on upper side, yellow-cream on underside; anal tufts cream to yellowish cream. Otherwise as male.

Male genitalia (Figs 46–50). Capsule longer (250–270 µm) than wide (200–220 µm). Vinculum without lateral lobes, ventral plate short (35–40 µm). Uncus with short thickened lateral lobes. Gnathos with two caudal, 35–40 µm long processes (Fig. 49). Valva (Figs 47, 48) 200–205 µm long, with numerous long chaetae; apical process weakly individualized; transtilla with very short sublateral processes. Juxta X-shaped (Fig. 48). Aedeagus (Fig. 50) 170 µm long; vesica without cornuti.

Female genitalia (Figs51–54). Total length 1055 µm. Apophyses anteriores (about 110 µm) much shorter than apophyses posteriores (about 145µm) (Fig. 52). Vestibulum relatively narrow, without sclerites. Accessory sac very small. Corpus bursae oval, 590–600 µm, covered with numerous pectinations and with long (360–375µm), strongly chitinized signa (Figs 53, 54).

Bionomics. Mines in leaves (Figs 7–9). Host-plants: Quercus spp., incl. Q. crassifolia Humb. & Bonpl. and Q. crispipilis Trel. (section Lobatae) in Guatemala (Figs 10, 11). Egg on upper side of the leaf. Larvae mine in February. Sinuous gallery of mine filled with blackish frass (Figs7–9). Larva pale green, with brownish intestine. Larval exit slit on upper side of the leaf. Cocoon (Fig. 30) whitish; length 2.4 mm, maximal width 1 mm. Adults emerged in March.

Distribution (Figs 1, 2). USA (from Cincinnati, Ohio and Pennsylvania to Texas) (Newton & Wilkinson 1982); Guatemala in montane mixed forests at elevation 1655–2500 m (Figs 3, 12).

Note. The specimens from Guatemala strongly vary in head markings (frontal tuft from fully black to yellowish cream in frontal part) and forewing markings (see figs 32, 33). However, the male and female genitalia fully correspond with those illustrated in Newton & Wilkinson (1982).