Family Adelidae Bruand, 1850

Description. Body small, wing expanse usually 10–26 mm. Head rough on vertex, covered with dense scales and hairs; ocelli absent; face usually covered with smooth broad scales. Compound eyes small to extremely large; eyes dimorphic in most species of the genera Adela and Nemophora with that of male obviously enlarged, even complete close to each other dorsally, and usually with facets in upper 2/3 of eye outwardly enlarged (Fig. 1A). Antennae usually longer than forewing in both sexs, up to 3 × of forewing length in male but relatively short in female; antennae shorter in the genus Cauchas, usually 0.5–1.2 × forewing length in both sexes; scape slightly swollen in some males; flagellum slender, filiform, usually fully covered prostrate scales, slightly weak in ventral surface; some species of Adela and Nemophora thinckened with large and raised scales at basal part, especially in female; pecten usually present, but absent in Cauchas, Adela with 1–3 long anteriorly projecting hook-pegs on 8–10 of the flagellum, and Nemophora usually with a posteriorly projecting simple pecten on each segment of 2–7 flagellum (Fig. 1B). Pilifers present. Labrum and mandible usually vestigial (Fig. 1D). Proboscis usually elongate, well developed, 1.5–2.5 × length of labial palpus (Fig. 1C); reduced in some African Ceromitia species, about equal to labial palpus; basal part usually scaled laterally. Maxillary palpi 2–5-segmented, directed forwardly or folded; in Nemophora, Adela, and Cauchas obviously vestigial, short, usually only with 2–3 segments (Fig. 1F); but in Nematopogon very slender, 5-segmented, segment IV the longest and folded together with segment V. Labial palpi 3-segmented with variable length, usually directed anteriorly or upwardly (Fig. 1E); segments II and III usually rough and covered with long haris.

Laterocervical sclerites with slender, elongate, lateral processes. Metafurca with dorsal apophyses well developed, arising perpendicular from mesal lamella free from secondary arms of metafurcasternum (Fig. 3). Forewing slender, lanceolate or subovate; radial with 5 veins, R 3 and R 4 usually stalked or free, R 5 usually joining to costa before the apex, but terminating on termen below apex in the Nematopogon group; accessory cell present; base of M faint, rarely forked within cell; 1A+2A with short basal fork (Fig. 2). Hindwing lanceolate, usually without color markings; Rs stalked with M 1 or M 1 stalked with M 2, 1A+2A also with short basal fork (Fig. 2). Male frenulum of a single long stout bristle, usually accompanied by several smaller setae along costal margin; female frenulum consisting of 3–4 smaller bristles in a row along base of costa. Legs with tibial spur pattern of 0-2-4; epiphysis present (Fig. 4).

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Abdomen with 8 segments in male and 7 in female, which are usually broader. Segment I usually vestigial, the middle of tergite I (T1) complete membranous; sternite I (S1) only a V- or U-shaped sclerite centrally. T7 and S7 of female triangular, with pointed tip. T8 of male near quadrate, with arcuate posterior margin; posterior margin of S8 concaved in the middle (Fig. 5). Male genitalia: Uncus well developed or vestigial. Vinculum well developed, usually V- or U-shaped. Valva triangular or near quadrate, without valvar pectinifer in Adela, Cauchas, Nemophora and partial Ceromitia, or with one or three valvar pectinifer in Nematopogon . Aedeagus with an elongate tube; cornuti usually present, apex sometimes also armed with large, exogenous spines or lamellae. Juxta slender, arrow-shaped (Fig. 6). Female genitalia: Ovipositor with a compressed, pointed apex usually minutely serrated along ventral keel. Apophyses posteriores and anteriores slender. Vestibulum membranous; vestibular usually well-developed, sclerotized. Bursa copulatrix and corpus bursae usually completely membranous, without signa (Fig. 7).

Remarks. Adelidae is a widely distributed family that occurs in all geographical regions except Antarctica and New Zealand (Heppner 1991; Janse 1945; Meyrick 1912a, b; Davis 1999), mainly in the Palaearctic, Oriental, and Afrotropical regions; however, the distribution of each genus is not uniform. For example, most Ceromiti a occur in Africa, and the genus Nemophora mainly occurs in the Palaearctic and Oriental regions. However, the genera Adela, Cauchas, and Nematopogon were mainly distributed in the Palearctic region. At the species level, the vast majority of Adelidae species are distributed in a single geographical region, except for a few Nemophora species, which are widespread in China.

Key to subfamilies and genera of Adelidae in China

1 Maxillary palpi with 2–3 segments; partial basal flagellum of male with hooked-pegs or spines; valva without pectinifer............................................................................................... 2/ Adelinae

- Maxillary palpi with 4–5 segments; basal flagellum of male without hook-pegs or spines; valva with pectinifer...................................................................................... Nematopogoninae / Nematopogon

2 Hindwing with Rs and M 1 separate; male antenna with 1–3 long anteriorly projecting hook-pegs on 8–10 of flagellum..................................................................................................... Adela

- Hindwing with Rs and M 1 stalked; male antenna with a short posteriorly projecting simple pecten on each segment of 2–7 flagellum................................................................................... Nemophora