Generic diagnosis

Adult .–Color white, yellow, brown, or golden; with white or golden hairs and scales emanating from setal warts; antennal segments usually with basal ring of white hairs. Forewing with distinctive pattern of transverse, longitudinal, zig-zag, or irregular bands, rows or spots of white, silver, brown, golden, blue or black, often metallic or iridescent, hairs and scales; many species with four patches of black scales along Cu1b; membrane of forewing usually with light brown pigmented areas (Fig. 3A). Eye size variable, often very large, especially in male, in which case interocular distance small (Haddock 1977, figs. 13-18). Labial palps reduced in both sexes. Midcranial sulcus present; mesopleural katepisternum truncate. Forewing (Fig. 3A) with forks I and V present, fork I with short petiole; fork of M petiolate; discoidal cell (d) short, broad; thyridial cell (th) short. Hind wing broad (i.e., anal region expanded) in male (Fig. 3B), narrow in female (Fig. 4); R and M atrophied basally and fork V deep (about equal in length to its petiole) in both sexes. Tibial spur formula 0-2-2. Abdominal haemo-branchial apparatus well developed (Schmid 1998, fig. 826).

Male genitalia (Fig. 1).–Abdominal segment IX with sternum completely absent; pleural region narrow; tergum somewhat produced posteriorly. Preanal appendages (pr. ap.) long and narrow, blunt or forked, with or without thin, blade-like, apicoventral projection and apical setae. Segment X highly modified, with thin, lightly sclerotized lateral processes situated very low, almost at level of inferior appendages; usually narrow and pointed; connected mesally by membrane and to bases of preanal appendages by long, thin, vertical sclerotized straps (possibly extended pleural region of segment X; these processes have been misinterpreted as posterolateral extensions of segment IX by some authors). Inferior appendages (inf. ap.) short; connected basally by narrow, sclerotized bridge; fused bases of inferior appendages perhaps forming the functional equivalent of sternum IX; each inferior appendage with basoventral digitate or quadrate setose process (often slightly asymmetrical on right and left sides of specimen) or large, flat, scoop-like process; apex of inferior appendage generally flat and truncate or pointed in lateral view; bearing rounded or truncate apicomesal lobe (possibly second article of inferior appendage) and many long, prominent setae. Phallic apparatus large, situated between inferior appendages; phallic apodeme short; phallic shield with long, curved, slender, generally capitate, external periphallic processes ("swan's neck processes" of Ross [1944] incorrectly considered by him and other authors to be mesobasal processes of the inferior appendages and by Haddock [1977] to be associated with segment X; see Morse [1975] for the correct interpretation of these processes); phallobase large, trough-like; endothecal membranes highly erectile, often bearing spine-like endothecal setae; phalicata absent or very lightly sclerotized; endophallic membranes erectile; phallotremal sclerite small, U-shaped in dorsal view.

Female genitalia (Fig. 2).–Very simple; appendages of segment X (X. ap.) long, narrow; valves (v.) short, lobe-like, situated ventrolaterally; pair of very short, digitate processes (d. p.) present midlaterally, below appendages of X.

Larva.–Head (Figs. 5A, B): narrow; ventral apotome short, triangular; subocular ecdysial line present (Fig. 5A); head setal pattern as in Fig. 5E, typical for family; mandibles short and wide, with short, rounded to pointed teeth; antennae long and slender. Thorax (Figs. 5A, B): pronotum with anterolateral corners delimited by ecdysial line; anterior and lateral margins entire (Fig. 5B), crenulate (Marlier 1964, plate 19, fig. 6), or with toothed lobes (Wiggins 1996, fig. 19.4G); mesonotum with pair of large medial sclerites, mesonotal sa3 sclerites small, oval; metanotum with small, oval sa3 sclerites, but otherwise without sclerites; thoracic setal pattern as in Fig. 5B (see also Wiggins 1996, fig. 19.4B). Head and thoracic sclerites with diagnostic spots or bands (Haddock 1977, figs. 26-33). Legs long and slender; hind tibia not subdivided; hind tibia and tarsus often with two parallel rows of long setae (Fig. 5A) or with ventral row of spine-like setae. Abdomen (Figs. 5A, D): lateral hump sclerite of abdominal segment I with round anterior portion bearing rows of fine microtrichia and with narrow, posterolateral, sclerotized extension (Fig. 5C); gills, when present, single, generally distributed as in Fig. 5A (see also Wiggins 1996, fig. 19.4A); lateral fringe present on segments III-VII; lateral tubercles present or VIII; ventral band of uniformly small spines beside anal opening (Fig. 5D), or spines absent in the position.

Larval case.–Made of mineral fragments or plant material (sometimes arranged in spiral or transverse rows) or both, occasionally entirely of silk; usually long, straight, and cylindrical, often with one or more twigs or conifer needles extending beyond one end; a few species build flattened cases of leaf discs (Marlier 1964, plate 16, fig. 7; plt. 17, figs. 1, 2; plt. 18, fig. 1; plt. 23, fig. 1; plt. 28, fig. 1; plt. 30, fig. 1; plt. 31, fig. 1; Roback 1966, figs. 128, 137, 154, 156, 163, 166; Wiggins 1996, fig. 19.4C)

Remarks.–Monophyly for the genus is supported by several synapomorphies including, in the male genitalia: (1) sternum IX atrophied; (2) ventrally positioned processes of segment X; (3) inferior appendages with basoventral processes; (4) long, slender, curved phallic shield strips; in the female genitalia by the general reduction and simplicity of external genitalic appendages, especially: (5) short, narrow appendages of X; (6) reduced, nub-like valves; and (7) presence of small, digitate, mid-lateral processes on segment IX. Finally, Morse (1981) placed Nectopsyche and the Old World genus Parasetodes Mac Lachlan in the Nectopsychini based on the shared atrophication of the stems of R and M in the hind wing (Morse 1981, fig. 1).