Nonnullidens Grant & Peters 1993

Kluge, Nikita J., 2013, Mayflies of the genus Nonnullidens Grant & Peters 1993 (Ephemeroptera: Leptophlebiidae) from New Guinea, Zootaxa 3722 (1), pp. 33-49 : 33-48

Nonnullidens Grant & Peters 1993

= Barba Grant & Peters 1993 , syn. n.

Type species: Thraulus hsui Peters & Tsui 1972 .

The genus Nonnullidens belongs to Atalophlebolinguata Kluge 2009 and has all characters of this taxon ( Kluge, 2009). Within Atalophlebolinguata, Nonnullidens is most closely related to Choroterpini Kluge 2012 and probably can be included in this tribe. It has the following characters of Choroterpini:

(1) Larval patella-tibial suture is lost on all legs; in contrast to larva, in imago and subimago patella-tibial suture usually retains the plesiomorphic condition, being present on middle and hind legs and absent on fore legs.

(2) Tergalii are bilamellate, each lamella with several apical processes.

(3) Fore wing with symmetrical MA fork ( Peters & Tsui, 1972: Figs 5, 8 ).

(4) On hind wing Sc terminates near middle of costal margin and borders base of more or less expressed costal projection.

(5) Imaginal and subimaginal claws of all legs are ephemeropteroid.

The first four characters are non-unique apomorphies, found in some non-related taxa, and the fifth one is a plesiomorphy ( Kluge, 2004).

More specific character of Choroterpini is a differentiation between tergalii of the first pair (which are more or less simplified) and tergalii of remaining II–VII pairs. Nonnullidens does not have this feature: its tergalii of all seven pairs have basically the same structure ( Figs 4–6 ); only selected representatives have simplified structure of tergalii of one or several anterior pairs, with ventral lamella non-fringed or lost ( Table 1). However, in observed species of Nonnullidens ( N. variegatus and N. niger ) tergalii of the first pair do not participate in rhythmical respiratory movements made by tergalii of other pairs, but are immovably directed backward. Possibly, this is connected with differentiation of tergalii, common with Choroterpini.

Apomorphy, which testifies about holophyly of Nonnullidens , is a shortened larval claw with diminished number of denticles ( Fig. 2 ) ( Grant & Peters, 1993). Another character, common for all species of Nonnullidens and allowing to separate it from most other taxa, is shape of tergalii: each of two lamellae bears usually more than three processes (in contrast to Choroterpes s.l.) and these processes arise only from distal part of lamella (in contrast to Thraulus ) ( Figs 4–6 ). However, the same shape of tergalii is found in some other, non-related leptophlebiid taxa.

Originally, the genus Nonnullidens Grant & Peters 1993 was established for two species— N. hsui ( Peters & Tsui 1972 [ Thraulus ]), described as male imagoes and larvae associated by hypodermal coloration, and N. billhilli Grant & Peters 1993 , known as larvae only. In the same paper, a genus Barba Grant & Peters 1993 was established for a single species B. mariae ( Peters & Tsui 1972 [ Thraulus ]), described as imagoes and larvae associated by hypodermal coloration ( Grant & Peters, 1993). To separate the genera Thraulus , Nonnullidens and Barba by imaginal characters, Grant & Peters (1993) used ratio between the wide and the narrow portions of gonostylus (i.e., 1st and 2nd gonostylus segments fused together). Actually, this ratio differs in closely related species N. niger and N. reductus ( Figs 39 and 45 ), and can vary individually ( Figs 18 and 21 ). Another character used by them to separate Nonnullidens and Barba , is the shape of the penis. Among Nonnullidens (= Barba ), two types of penis are found: one penis type, with a funnel-shaped apical widening, occurs in N. hsui , N. variegatus sp. n. and N. depapricus sp. n. ( Figs 17–22 , 28 ); another penis type, with obliquely truncate apex, occurs in N. mariae , N. niger sp. n. an N. reductus sp. n. ( Figs 39 , 46 ). However, all other imaginal and larval characters do not correlate with such division based on penis structure ( Table 1). This makes me synonymize the generic names Nonnullidens and Barba and to move the species mariae [ Thraulus ] from Barba to Nonnullidens — Nonnullidens mariae comb.n.

Distribution. New Guinea.

Species composition. N. hsui ( Peters & Tsui 1972 [ Thraulus ]) (type species of Nonnullidens ); N. mariae ( Peters & Tsui 1972 [ Thraulus ]) (type species of Barba ); N. billhilli Grant & Peters 1993 ; N. variegatus sp. n.; N. depapricus sp. n.; N. niger sp. n.; N. reductus sp. n.

Nonnullidens variegatus Kluge , sp. n.

( Figs 1–22 , 51 )

Material. Holotype: L-S-I ♂ {specimen [VIII] (7)}: Indonesia, prov. Papua, Baliem Valley, river Elagaima , 19.VIII.2012, coll. N. Kluge & L. Sheyko. Paratypes: the same locality, 15–19.VIII.2012: 2 L-S-I ♂ , 1 L-S/I ♂, 3 L- S-I ♀, 2 L-S ♂, 2 L-S ♀, 125 larvae.

Larva. CUTICULAR COLORATION: Light ocher, only dorsal part of head and thorax with brown. Lateral parts of mandibles diffusively shaded with brown. Pronotum and mesonotum either brown, or laterally brown and medially light ocher; fore protoptera brown with lighter veins (both concave and convex). Legs light ocher, either unicolor, or femur with lighter middle part. Abdomen unicolor light ocher.

HYPODERMAL COLORATION (well visible through light cuticle and determines general color): Head and thorax with ocher and brown markings. Legs pale, each femur with two contrasting, brown bands—at middle and close to apex ( Figs 7–9 ). Hypodermal abdominal coloration differs in male and female beginning in early larval instars: in male, anterior terga light ocher, posterior terga light ocher with brown lateral markings (as in imago— Fig. 13 ); in female, all terga brown, with light ocher anterior and posterior margins and with wide or narrow light ocher median stripe (as in imago— Fig. 14 ). Sterna ocher, either unicolor, or with brown maculae. Tergalii dark brown.

SHAPE AND SETATION: Labrum ( Fig. 1 ) wider than clypeus; median incision with slightly expressed denticles; both transverse setal rows dense and irregular: in distal row, setal bases are situated close one to another and form a stripe 3 of 4 setal bases width; in proximal row, setal bases are situated close one to another and form a stripe 2 of 3 setal bases width. Outer margin of mandible evenly convex ( Fig. 3 ). Maxilla similar to that on N. hsui ( Grant & Peters, 1993: Fig. 53 ), with 25–30 pectinate setae in subapical row. Hypopharynx similar to that of N. hsui ( Grant & Peters, 1993: Fig. 51 ). Labium similar to that on N. hsui ( Grant & Peters, 1993: Fig. 59), with dorsal surface of segment 3 of palpi with 2–3 large setae.

Femora of all legs narrowed apically, fore femur widest near base, middle and hind femora widest in middle ( Figs 7–9 ). Femur of each leg has long spine-like setae on outer margin numerous, dense, irregularly arranged; dorsal surface with smaller spine-like setae; inner margin with a regular row of small spine-like setae ( Fig. 10 ). Patella-tibial suture absent on all legs. Fore tibia with dense, irregularly situated, pectinate spine-like setae on inner side. Middle tibia with fewer, irregularly situated, spine-like setae on inner side. Hind tibia with irregularly situated, spine-like setae on inner and posterior sides, with irregularly situated, long, spine-like setae on anterior side and with irregular row of long, spine-like setae on outer margin. Tarsus with row of spine-like setae on inner side. Claw with 4–5 denticles, most distal of which is largest and situated on convexity ( Fig. 2 ).

Abdomen without pointed posterolateral spines; blunt posterolateral projections on segments VIII and IX. Abdominal terga IX and X with small pointed denticles on hind margin; other terga and sterna without denticles. All tergalii I–VII bilamellate; each lamella truncate, with processes on apex. Tergalius I narrowest, with 3–7 processes on dorsal lamella and 2–4 processes on ventral lamella ( Fig. 4 ). Tergalii II–VII with 8–11 processes on dorsal lamella and 6–7 processes on ventral lamella; length of tergalii decreases from tergalius III to tergalius VII ( Figs 5, 6 ). In male larva of last instar, protopenes short and truncate ( Fig. 22 ), much shorter than subimaginal penis.

Subimago. CUTICULAR COLORATION: Head colorless. Pronotum colorless. Mesonotum with brown pattern as in Fig. 51 : the pigmented area anteriad of mesonotal suture ("a") contrastingly darker than the nonpigmented area posteriad of mesonotal suture ("p"). Thoracic sterna and pleura colorless with a few brown markings. Legs nearly entirely colorless; femur with brown tip and brownish longitudinal stripes at outer and inner margins; tibia with brown base and brownish longitudinal stripe at outer margin. Abdomen, genitals and caudalii colorless.

HYPODERMAL COLORATION: Similar to imago (see below).

TEXTURE: Tarsi of all legs of male and female covered with microtrichiae, like other parts of legs and body.

Imago, male. Head brown. Upper eyes not elevated, brownish-orange. Thorax on all sides (dorsal, lateral and ventral) with brown and ocher maculation. On fore wing basal sclerites brownish, veins ocher, membrane colorless; pterostigma with 8–12 simple oblique crossveins. Hind wing with basal sclerites brownish; costal process stretched and pointed ( Fig. 16 ). Fore leg: femur reddish brown with two dark brown bands—at middle and close to apex; tibia reddish brown with dark brown apex; tarsus colorless. Middle and hind legs: femur pale ocher with distal 1/3 reddish brown and with two dark brown bands—at middle and close to apex; tibia light reddishbrown in proximal part and colorless in distal part; tarsus colorless. Middle and hind legs with patella-tibial suture well-developed; tarsus with apical thorn on each of 4 proximal segments. Abdomen pale ocher, terga with brown makings ( Fig. 13 ): Each tergum I–VIII with a pair of small blackish-brown spots (on terga I–VII they are situated just anteriad of tergalii insertions). Mediad of them, a pair of lighter brown spots close to hind margin. Mediad of them, a pair of longitudinal spots close to anterior margin; they are absent on anterior terga, small on middle terga and large on terga VII–IX. Abdominal sterna either without markings, or with brown nerve ganglia. Styliger pale ocher, gonostyli colorless. Posterior margin of styliger either with a pair of prominent semicircular convexities and incision between them ( Fig. 18 ), or nearly straight ( Fig. 21 ). Internal penial arms light brown, external penes light yellowish. Penis lobes separated nearly to base; each apically sharply widened like a funnel; lateral sides of penis lobes smooth, without spines; a few small translucent spines present on funnel-shaped widening, on its side opposed to the opening ( Fig. 17 ). In subimago, penis has exactly the same size and structure as in imago, with the same shape of funnel-like widening and its apical concavity; larval protopenis is much shorter and simple ( Fig. 22 ). Caudalii pale, with contrasting dark brown joinings of each segment.

Imago, female. Coloration similar to that of male, except for abdominal terga: each tergum I–IX has middle part nearly entirely brown, with pale ocher anterior and posterior margins and sometimes with narrow median pale ocher stripe ( Fig. 14 ). Posterior margin of sternum IX convex, without median incision.

Egg ( Figs 11, 12 ). Oval, 0.17 mm length. Most of surface with regularly arranged groups of tubercles. Each tubercle has simple, irregularly-oval shape. Each group has 1 or 2 tubercles in middle; around them 6–8 tubercles inclined toward middle ones. One side of egg has a large area lacking tubercles and bearing 2 micropiles located on equator ( Fig. 11 ). This sculpture of chorion becomes visible only after heating egg in lactic acid. On eggs preserved in ethanol, all tubercles are hidden in concavities, being not projected above egg surface.

Dimension. Fore wing length 7–8 mm.

Habitat. Larvae were collected at 1700 m.a.s.l., in a valley with cool climate, in a mountain river of medium size, with stony bottom and fast current. N. variegatus is one of the dominant species, together with several undescribed species of Labiobaetis and Papuanatula ; more rare mayfly species in this river are N. niger , N. mariae , Thraulus sp. , Caenis sp. and Mystaxiops venatoris McCafferty & Sun 2005 .

Comparison. Imago of N. variegatus sp. n. is similar to N. hsui in shape of penis, which has apical funnel-like widening. In contrast to N. hsui , whose abdominal terga 1–8 have large triangular posterolateral marks ( Peters & Tsui, 1972: Figs 28 , 29 ), in N. variegatus sp. n. anterior abdominal terga have small posterolateral markings, and posterior terga have two pairs of markings ( Fig. 13 ).

Larva of N. variegatus sp. n. is similar to N. hsui in shape of labrum ( Fig. 1 and Peters & Tsui, 1972: Figs 43, 44 ). In contrast to N. hsui , whose tergalii have dorsal lamella ovate and fringed, and ventral lamella lanceolate ( Peters & Tsui, 1972: Fig. 54; Grant & Peters, 1973: Fig. 77), in N. variegatus sp. n. both lamellae are truncate and fringed apically ( Figs 4–6 ).

Larva of N. variegatus sp. n. has shape of tergalii similar to that of N. billhilli (Grant & Peters, 1973: Fig. 78); in contrast to N. billhilli , whose fore femora lack transverse brown bands, in N. variegatus sp. n. all femora have equally contrasting transverse brown bands ( Figs 7–9 ).

Nonnullidens depapricus Kluge , sp. n.

( Figs 23–31 )

Material. Holotype: immature male larva of last instar: mountain river 2 km NE from Depapre (western coast of Cyclop Mountains), 25–28.VIII.2012, coll. N. Kluge & L. Sheyko.

Larva. CUTICULAR COLORATION: Light ocher with diffusive brown maculae: at least lateral parts of mandibles brown.

HYPODERMAL COLORATION: (well visible through light cuticle and determines general color): Head and thorax ocher, with brown markings. Legs ocher with brown markings ( Figs 29–31 ): Femora with brown maculae at apex and at middle; on fore femur apical macula is especially large, outer and inner margins bordered with brown; on middle femur maculae are smallest. Each tibia with brown apex and brown longitudinal line on inner side. Abdominal terga entirely dark brown. Each abdominal sternum I–VIII ocher, with a pair of large brown sublateral maculae. Subimaginal gonostyli, developing under larval cuticle, colorless in proximal half and dark brown in distal half.

SHAPE AND SETATION: Labrum as in N. reductus ( Fig. 41 ): as wide as clypeus, with base narrower than clypeus; median incision with slightly expressed denticles; both transverse setal rows regular; in distal row bases of setae contiguous; in proximal row bases of setae spaced. Outer margin of mandible truncate (as in Fig. 42 ). Maxilla with 22 pectinate setae in subapical row.

Femora of all legs narrowed apically, fore femur widest near base, middle and hind femora widest in middle ( Figs 29–31 ). Femur of each leg has long spine-like setae on outer margin forming one regular marginal row (as in Fig. 35 ) and sometimes also submarginal row; inner margin with sparse very small spine-like setae. Patella-tibial suture absent on all legs. Fore tibia with irregularly situated, pectinate spine-like setae on inner side. Middle tibia with one sparse row of small spine-like setae on anterior side near inner margin and with a few minute setae on inner side. Hind tibia with irregularly situated, spine-like setae on inner and posterior sides, with one row of larger spine-like setae on anterior side and a sparse row of spine-like setae on outer margin. Tarsus with row of spine-like setae on inner side. Claw with 4–5 denticles, most distal of which largest and situated on convexity (as in Fig. 2 ).

Abdomen without pointed posterolateral spines; blunt posterolateral projections on segments VIII and IX. Abdominal terga IX and X with small pointed denticles on hind margin; other terga and sterna without denticles. Tergalii I–IV unilamellate (lack ventral lamella), tergalii V –VII with non-branched, thread-like ventral lamella ( Figs 23–26 ). In the single specimen examined, dorsal lamellae of tergalii I–VII have following number of apical processes: 3, 4, 5, 6, 5, 4, 3. Protopenis short and wide ( Fig. 28 ).

Subimago. Unknown.

Imago, male. Unknown. Coloration of legs and abdomen should be the same as hypodermal coloration of larva (see above). Judging by hypodermal brown pigmentation of pterostigma area of fore protopteron, imaginal pterostigma can be colored. Hind wing with costal process stretched and pointed ( Fig. 27 ). Judging by subimaginal genitals developing under larval cuticle, penis has the same structure as in N. variegatus : penis lobes separated nearly to base; each penis lobe apically sharply widened like a funnel; larval protopenis much shorter and simple ( Fig. 28 ).

Imago, female. Unknown.

Egg. Unknown.

Dimension. Length of last instar larva 4 mm.

Habitat. Larvae were collected at 50 m. a.s.l., in coastal area with hot climate, in a mountain forest river with stony bottom and very warm water (constantly 30ºC).

Comparison. N. depapricus differs from all other species by absence of ventral lamella on first four pairs of tergalii. Its genital structure is the same as in N. hsui and N. variegatus ; male of N. depapricus differs from N. hsui and N. variegatus by dark brown abdominal terga.

Nonnullidens niger Kluge , sp. n.

( Figs 32–40 , 49 , 52 )

Material. Holotype: L-S-I ♂ {specimen [VIII](3)}: Indonesia, prov. Papua, Baliem Valley, river Elagaima , 19.VIII.2012, coll. N. Kluge & L. Sheyko. Paratypes: the same locality, 15–19.VIII.2012: 1 L-S-I ♂, 2 L-S ♂, 1 L- S/I ♀, 5 mature larvae .

Larva. CUTICULAR COLORATION: Light ocher, only dorsal part of head and thorax with brown. Lateral parts of mandibles diffusively shaded with brown. Pronotum and mesonotum either brown, or laterally brown and medially light ocher; fore protoptera brown. Legs unicolor light ocher. Abdomen unicolor light ocher.

HYPODERMAL COLORATION: (well visible through light cuticle and determines general color): Head and thorax dorsally brown with ocher markings, median part of mesonotum ocher. Each femur brown, with base pale ocher, sometimes with longitudinal lighter and darker stripes, but without transverse bands; tibia either ocher, or brownish, or with darkened apex. Abdominal terga in both sexes dark brown, with or without lighter median stripe. Sterna either ocher, or brown, or maculated. Tergalii dark brown.

SHAPE AND SETATION: Labrum as in N. reductus ( Fig. 41 ): as wide as clypeus, with base narrower than clypeus; median incision with slightly expressed denticles; both transverse setal rows regular; in distal row bases of setae contiguous; in proximal row bases of setae spaced. Outer margin of mandible truncate (as in Fig. 42 ). Maxilla similar to that on N. hsui ( Grant & Peters, 1993: Fig. 53 ), with 23–25 pectinate setae in subapical row. Hypopharynx similar to that of N. hsui ( Grant & Peters, 1993: Fig. 51 ). Labium similar to that on N. hsui ( Grant & Peters, 1993: Fig. 59), with dorsal surface of segment 3 of palpi with 2–5 large setae.

Femora of all legs narrowed apically, fore femur widest near base, middle and hind femora widest in middle (as in Figs 7–9 ). Femur of each leg has long spine-like setae on outer margin forming one regular marginal row and one nearly regular submarginal row; dorsal surface with small spine-like setae; inner margin with sparse small spine-like setae ( Fig. 35 ). Patella-tibial suture absent on all legs. Fore tibia with irregularly situated, pectinate spine-like setae on inner side. Middle tibia with one sparse row of small spine-like setae on anterior side near inner margin and with thinner short setae on inner side. Hind tibia with irregularly situated, spine-like setae on inner and posterior sides, with one row of larger spine-like setae on anterior side and a sparse row of spine-like setae on outer margin. Tarsus with row of spine-like setae on inner side. Claw with 4–5 denticles, most distal of which is largest and situated on convexity (as in Fig. 2 ).

Abdomen without pointed posterolateral spines; blunt posterolateral projections on segments VIII and IX. Abdominal terga IX and X with small pointed denticles on hind margin; other terga and sterna without denticles. All tergalii I–VII bilamellate; each lamella truncate, with processes on apex. Tergalius I narrowest, with 3–4 processes on dorsal lamella and 2–3 processes on ventral lamella ( Fig. 32 ). Tergalii II–VII with 5–8 processes on dorsal lamella and 5–7 processes on ventral lamella; length of tergalii decreases from tergalius III to tergalius VII ( Figs 33, 34 ). Larval protopenis long, with distal part of gonoduct lined by cuticle ( Fig. 40 ); on exuviae shed at larval/subimaginal molt, proximal half of larval protopenis is crumpled and inverted, so that protopenis looks twice shorter.

Subimago. CUTICULAR COLORATION: Head colorless. Pronotum colorless. Mesonotum with brown pattern as in Fig. 52 : the pigmented area anteriad of mesonotal suture ("a") is not much darker than the area posteriad of mesonotal suture ("p"). Thoracic sterna and pleura colorless. Legs neatly entirely colorless; femur with brownish tip and tibia with brownish base. Abdomen, genitals and caudalii colorless.

HYPODERMAL COLORATION: Similar to imago (see below).

TEXTURE: Tarsi of all legs of male and female covered with microtrichiae, like other parts of legs and body.

Imago, male. Head brown. Upper eyes not elevated, brownish-orange. Thorax on all sides (dorsal, lateral and ventral) dark brown, only articulatory membranes lighter. On fore wing basal sclerites brownish, veins ocher, membrane colorless; pterostigma with 7–10 simple oblique crossveins. Hind wing with basal sclerites brownish; costal process stretched and pointed. On fore leg femur and tibia dark brown, tarsus lighter. On middle and hind legs femur dark brown except basal 1/4, which is contrastingly lighter; tibia dark brown; tarsus lighter. Middle and hind legs with patella-tibial suture well-developed; tarsus with apical thorn on each of 4 proximal segments. All abdominal terga dark brown, sterna a little lighter brown. Each tergum II–VIII with lighter markings, among which are a pair of submedian maculae adjacent to anterior margin of tergum. Each sternum II–VIII with a pair of similar submedian light maculae. Styliger and gonostyli brown. Posterior margin of styliger varies from shallowly convex ( Fig. 39 ) to shallowly concave ( Fig. 49 ). Penis brown. Penis lobes separated nearly to base; each penis lobe obliquely truncated, with small blunt apical projection directed caudally-laterally-ventrally; lateral sides of penis lobes with small spines directed proximally ( Fig. 39 ). In subimago, penis has exactly the same structure and size as in imago; larval protopenis is also long ( Fig. 40 ). Caudalii pale, with contrasting dark brown joinings of each segment.

Imago, female. Coloration similar to that of male. Posterior margin of sternum IX convex, without median incision.

Egg. 0.19 mm, oval. Surface smooth, without visible relief.

Dimension. Fore wing length 6–7 mm.

Habitat. Larvae were collected together with N. variegatus (see above).

Comparison. N. niger sp. n. differs from N. variegatus by penis structure, hypodermal coloration, shape and setation of labrum, shape of mandibles and setation of larval legs. Penis structure of N. niger is similar to that of N. mariae . In contrast to N. mariae , whose femora are light with dark bands, and abdomen of male imago is white with brown maculation ( Peters & Tsui, 1972), in N. niger femora are dark brown without bands, and abdomen of both sexes is dark brown. Larva of N. niger , besides hypodermal coloration (which is the same as in imago), differs from N. mariae by shape of tergalii, which in N. mariae are fimbriate in apical 1/3, and in N. niger fimbriate only apically ( Figs 32–34 ). Larva of N. niger sp. n. has shape of tergalii similar to that of N. billhilli (Grant & Peters, 1973: Fig. 78); in contrast to N. billhilli , whose middle and hind femora have transverse brown bands, in N. niger sp. n. all femora are dark without bands.

Nonnullidens reductus Kluge , sp. n.

( Figs 41–48 , 50 , 53 )

Material. Holotype: L-S-I ♂ {specimen [II](6)}: Indonesia, prov. Papua, area of Port Numbay (Jayapura), Waena , 11.VIII.2012, coll. N. Kluge & L. Sheyko. Paratypes: the same locality, 9–13.VIII.2012: 5 L-S ♂ , 1 L-S-I ♀, 3 L- S ♀, 15 larvae. Mountain river 2 km NE from Depapre (western coast of Cyclop Mountains), 25–28.VIII.2012, coll. N. Kluge & L. Sheyko: 1 larva .

Larva. CUTICULAR COLORATION: Light ocher, only dorsal part of head and thorax with brown. Lateral parts of mandibles diffusively shaded with brown. Pronotum and mesonotum either brown, or laterally brown and medially light ocher; fore protoptera brown. Legs light ocher unicolor. Abdomen unicolor light ocher.

HYPODERMAL COLORATION: (well visible through light cuticle and determines general color): Head and thorax dorsally brown with ocher markings, median part of mesonotum ocher. Each femur brown, with base pale ocher, without transverse bands; tibia either ocher, or brownish, or with darkened apex. Abdominal terga in both sexes dark brown, with or without lighter median stripe. Sterna either ocher, or brown, or maculated. Tergalii dark brown.

SHAPE AND SETATION: Labrum ( Fig. 41 ) as wide as clypeus, with base narrower than clypeus; median incision with slightly expressed denticles; both transverse setal rows regular; in distal row bases of setae contiguous; in proximal row bases of setae spaced. Outer margin of mandible truncate ( Fig. 42 ). Maxilla similar to that on N. hsui ( Grant & Peters, 1993: Fig. 53 ), with 26–27 pectinate setae in subapical row. Hypopharynx similar to that of N. hsui ( Grant & Peters, 1993: Fig. 51 ). Labium similar to that on N. hsui ( Grant & Peters, 1993: Fig. 59), with dorsal surface of segment 3 of palpi with 1–3 large setae.

Femora of all legs narrowed apically, fore femur widest near base, middle and hind femora widest in middle (as in Figs 7–9 ). Femur of each leg has long spine-like setae on outer margin forming one regular marginal row (as in Fig. 35 ) and sometimes also submarginal row; inner margin with sparse very small spine-like setae. Patella-tibial suture absent on all legs. Fore tibia with irregularly situated, pectinate spine-like setae on inner side. Middle tibia with one sparse row of small spine-like setae on anterior side near inner margin and with a few minute setae on inner side. Hind tibia with irregularly situated, spine-like setae on inner and posterior sides, with one row of larger spine-like setae on anterior side and a sparse row of spine-like setae on outer margin. Tarsus with row of spine-like setae on inner side. Claw with 4–5 denticles, most distal of which is largest and situated on convexity (as in Fig. 2 ).

Abdomen without pointed posterolateral spines; blunt posterolateral projections on segments VIII and IX. Abdominal terga IX and X with small pointed denticles on hind margin; other terga and sterna without denticles. Tergalii of the first pair unilamellate (lack ventral lamella), with 3 processes at apex ( Fig. 43 ). Tergalii II–VII bilamellate; each lamella truncate; dorsal lamella with 5–7 processes, ventral lamella with 2–4 processes ( Fig. 44 ); length of tergalii decreases from tergalius III to tergalius VII. Larval protopenis long, with distal part of gonoduct lined by cuticle (as in Fig. 40 ); on exuviae shed at larval/subimaginal molt, proximal half of larval protopenis is crumpled and inverted, so that protopenis looks twice shorter.

Subimago. CUTICULAR COLORATION: Head colorless. Pronotum colorless. Mesonotum with brown pattern as in Fig. 53 : the pigmented area anteriad of mesonotal suture ("a") is not darker than the area posteriad of mesonotal suture ("p"). Thoracic sterna and pleura colorless. Legs nearly entirely colorless; femur with brownish tip and tibia with brownish base. Abdomen, genitals and caudalii colorless.

HYPODERMAL COLORATION: Similar to imago (see below).

TEXTURE: Tarsi of all legs of male and female covered with microtrichiae, like other parts of legs and body.

Imago, male. Head brown. Upper eyes not elevated, brownish-orange. Thorax on all sides (dorsal, lateral and ventral) dark brown, only articulatory membranes lighter. On fore wing basal sclerites brownish, veins ocher, membrane colorless; pterostigma with 7–10 simple oblique crossveins. Hind wing with basal sclerites brownish; costal process stretched and pointed; distal part of hind wing (distad of costal projection) shortened ( Fig. 48 ). On fore leg femur dark brown; tibia pale with base (patella) brown and apex brownish; tarsus pale. On middle and hind legs femur dark brown except basal 1/4, which is contrastingly lighter; tibia and tarsus lighter. Middle and hind legs with patella-tibial suture well-developed; tarsus with apical thorn on each of 4 proximal segments. All abdominal terga dark brown, sterna a little lighter brown. Each tergum II–VIII with lighter markings, among which a pair of submedian maculae adjacent to anterior margin of tergum (as in N. niger — Fig. 36 ). Each sternum II–VIII with a pair of similar submedian light maculae. Styliger and gonostyli brown. Posterior margin of styliger with truncate projection whose sides armed by sclerotized brown ridges ( Fig. 45 , 50 ). Penis brown. Penis lobes separated nearly to base; each penis lobe obliquely truncated, with small blunt apical projection directed caudally-laterallyventrally; lateral sides of penis lobes with small spines directed proximally ( Fig. 46 ). In subimago, penis has exactly the same structure and size as in imago; larval protopenis is also long (as in Fig. 40 ). Caudalii pale, with contrasting dark brown joinings of each segment.

Imago, female. Coloration similar to that of male. Posterior margin of sternum IX convex, without median incision.

Egg. 0.16 mm, oval. Surface smooth, without visible relief.

Dimension. Fore wing length 5–6 mm.

Habitat. Larvae were collected at 200 m. a.s.l., in costal area with hot climate, in a mountain forest river with stony bottom. Besides N. niger , there were collected several undescribed species of Labiobaetis and Papuanatula , Mystaxiops venatoris , undescribed species of Centroptella , Prosopistoma sedlaceki Peters 1967 and Caenis sp.

Comparison. N. reductus is most closely related to N. niger and differs from other species by the same characters as N. niger (see above). Larva of N. reductus differs from N. niger by absence of ventral lamella on tergalii of first pair ( Fig. 43 ). Imago of N. reductus differs from N. niger by light tibiae; shorter 1st segment of gonostylus and peculiar shape of styliger margin ( Figs 45 and 50 ; compare with Figs 39 and 49 ); shorter distal part of hind wing and hind protopteron ( Figs 47, 48 ; compare with Figs 37, 38 ).

Figures

FIGURES 4–10. Nonnullidens variegatus, larva. 4–6, tergalii of I, II and VII pairs (ventral lamella turned back); 7–9, outline and hypodermal coloration of fore, middle and hind legs (setae not shown); 10, femur of middle leg (hypodermal coloration not shown) (4–6, holotype).

FIGURES 1–3. Nonnullidens variegatus, larva. 1, labrum, dorsal view (setae of transverse rows not shown, their bases shown as dots and levels of their apices shown by interrupted lines); 2, pretarsal claw; 3, left mandible (2, holotype).

FIGURES 39–40. Nonnullidens niger. 39, genital of male imago, ventral view; 40, posterior margin of sternum IX of male larva of last instar and larval protopenis, dorsal view.

FIGURES 45–48. Nonnullidens reductus (holotype). 45, styliger and gonostyli, ventral view; 46, penis, ventral view; 47, hind protopteron of larva; 48, hind wing of male imago.

FIGURES 17–22. Nonnullidens variegatus. 17, 20, apex of penis of male imago, ventral view; 18, 21, genitals of male imago, ventral view; 19, exuviae of subimaginal gonostylus; 22, posterior margin of sternum IX of male larva of last instar and larval protopenis (19–22, holotype).

FIGURES 23–28. Nonnullidens depapricus, male larva (holotype). 23–26, tergalii of I, IV, V and VII pairs; 27, hind protopteron (developing subimaginal wing shown by interrupted line); 28, protopenis (developing subimaginal penis shown by interrupted line).

FIGURES 51–53. Subimaginal exuviae of mesonotum. 51, Nonnullidens variegatus, female; 52, Nonnullidens niger, male (holotype); Nonnullidens reductus, male (holotype). Abbreviations: a, pigmented area antediad of mesonotal suture; p, area posteriad of mesonotal suture.

FIGURES 11–16. Nonnullidens variegatus. 11–12, egg; 13, abdominal terga IV–VII of male imago, spread on slide; 14, abdominal tergum V of female imago, spread on slide; 15, hind protopteron of larva; 16, hind wing of male imago (13, 15, 16, holotype).

FIGURES 29–31. Nonnullidens depapricus, male larva (holotype). 29, fore leg; 30, middle leg; 31, hind leg.

FIGURES 41–44. Nonnullidens reductus, larva. 41, labrum, dorsal view (setae of transverse rows not shown, their bases shown as rings and levels of their apices shown by interrupted lines); 42, left mandible; 43, 44, tergalii of I and II pairs (ventral lamella turned back) (43, 44, holotype).

FIGURES 32–38. Nonnullidens niger (holotype). 32, 33 tergalii I and II pairs (ventral lamella turned back); 34, tergalius of VII pair; 35, femur of middle leg (hypodermal coloration not shown); 36, abdominal tergum V of male imago, spread on slide; 37, hind protopteron of larva; 38, hind wing of male imago.

FIGURES 49–50. Genitals of male imagoes, ventral view. 49, Nonnullidens niger (holotype); 50, Nonnullidens reductus (nonreared specimen).