(Figs. 1 –17)
Type material. Holotype male with pupal exuviae (SUM-IC-T0491), JAPAN: Shizuoka, Suruga-ku, spring in Udo Hills, 8.x. 1997 (emerged 13.x. 1997). Paratypes. JAPAN: Shizuoka, Suruga-ku, Udo Hills, 3 males with 3 pupal exuviae (SUM-IC-T0492–T0494), 8.x. 1997 (emerged 15 and 20.x. 1997); 1 male (SUM-IC-T0495) and 1 pupa (SUM-IC-T0496), as previous except 19.x. 1997; 2 females with 2 pupal exuviae (SUM-IC-T0497 and T0498), as previous except 5.xi. 1997 (emerged 7 and 9.xi. 1997); 1 female with pupal exuviae (SUM-IC-T0499), as previous except 20.ix. 1997 (emerged 27.ix. 1997); 1 male with pupal exuviae (SUM-IC-T0500), as previous except 10.iv. 1998 (emerged 14.iv. 1998); 1 male (SUM-IC-T0501), as previous except 26.x. 2001; 1 male with pupal exuviae (SUM-IC-T0502) and 1 female with pupal exuviae (SUM-IC-T0503), as previous except 30.ix. 2002 (emerged 25.x. and 11.xi. 2002); Fukushima, Iwaki, Yaguki, spring, 1 female with pupal and larval exuviae (SUM- IC-T0504) and 1 pupal exuviae (SUM-IC-T0505), 4.v. 2008 (emerged 28.v. 2008).
Derivatio nominis. From the Latin parallelus, referring to the parallel-sided gonostylus of the male hypopygium.
Description. Male (n = 8). Total length 3.0– 3.6, 3.3 mm.
Coloration. Generally yellow to pale brown. Head yellowish; eyes iridescent in alive specimen. Thorax darkened on prescutellar area, anepisternum, preepisternum and postnotum; scutal vittae indistinct. Abdominal tergites II–VI each with transverse dark band anteriorly; T.VII–IX and gonocoxite of hypopygium mostly darkened. Wing (Fig. 1) with two transverse dark bands; distal band somewhat incomplete. Cross-veins RM and MCu, and FCu darkened. Legs generally yellowish, slightly darkened preapically on femur and subbasally on tibia.
Head. Temporals 29 –38, 34 (7), multiserial. AR 1.6–1.9. Clypeus trapezoidal with 22 –38, 30 setae. Lengths of palpomeres 1–5 (µm): 43 –55, 50 (6); 58 –65, 60 (6); 118–135, 127 (6); 213–233, 225 (6); 225–260, 421 (5). Pm 5 1.0– 1.1 (5) times as long as Pm 4.
Thorax. Antepronotals 7 –12, 10, laterally. Acrostichals 74 –95, 85 (6), bi- to multiserial, diverging posteriorly; dorsocentrals 42 –58, 50 (6), multiserial; humerals 10 –20, 13 (6), multiserial; prealars 19 –31, 27 (7), multiserial; supraalars 1; anepisternals 0–5, 2; preepisternals 1 –5, 3; scutellars 24 –36, 30 (5), multiserial; postnotals 5 –9, 8. Small scutal tubercle occasionally present, 25–50 (2) µm long and 3–5 (2) µm high.
Wing. Length 2.3–2.6, 2.4 (7) mm. Membrane with dense macrotrichia. VR 0.90–0.94 (7). Squama with 25 – 35, 30 (7) setae.
Legs. Spur Ti I 55 –63, 59 µm long, with 10 –13, 12 (7) lateral teeth. Spurs Ti II 63 –73, 69 and 48 –55, 51 µm long, with 11 –14, 13 and 11 –13, 12 lateral teeth, respectively; inner spur 1.3–1.4 times as long as outer spur. Spurs Ti III 65 –78, 71 and 45 –53, 49 µm long, each with 11 –14, 12 (5) lateral teeth; inner spur 1.4–1.5 times as long as outer spur; comb Ti III consisting of 7 –9, 8 bristles. Claw pointed apically with 2 long and 2 or 3 short baso-ventral spines; pulvilli very reduced. Lengths and proportions of leg segments as in Table 1.
Hypopygium (Fig. 2). Tergite IX with 7 –15, 11 posterior setae. Gonocoxite 183–205, 193 (7) µm long, and 2.1–2.4 (7) times as long as broad in middle. Gonostylus 98–108, 103 (7) µm long, parallel-sided for most of its length, with blunt apex; HR 1.8 –2.0 (7). Phallapodeme straight or slightly curved.
Female (n = 5). Total length 2.4–2.7, 2.5 (3) mm.
Coloration. Similar to male.
Head. Temporals 30 –38, 34 (4). Antenna with terminal flagellomere as long as or slightly longer than preceding 3 segments together; AR 0.23–0.25 (4). Clypeus with 38 –50, 45 (4) setae. Lengths of palpomeres 1–5 (µm): 45 –50, 48 (3); 55 –60, 58 (3); 123–160, 136 (3); 215–250, 234 (3); 233–250 (2). Pm 5 1.1 (2) times as long as Pm 4.
Thorax. Antepronotals 7 –10, 8 (4) laterally; acrostichals 75 –108, 92; dorsocentrals 42 –66, 55; humerals 25 – 35, 30 (4); prealars 30 –43, 35 (4); supraalars 1 (3); anepisternals 1 –6, 4 (4); preepisternals 4 –7, 6 (4); scutellars 34 – 51, 42 (4); postnotals 7 –12, 9 (4). Scutal tubercle occasionally present, 4–5 (2) µm high.
Wing. Length 2.4–2.6, 2.5 (3) mm. VR 0.92–0.95 (4). Squama with 29 –36, 33 (3) setae.
Legs. Spur Ti I 58 –65, 61 (4) µm long, with 11 –13, 12 (4) lateral teeth. Spurs Ti II 69 –78, 74 (4) and 53 –60, 55 (4) µm long, with 14 –16, 15 (4) and 13 –15, 14 (4) lateral teeth, respectively; inner spur 1.3–1.4 (4) times as long as outer spur. Spurs Ti III 70 –88, 78 (4) and 48 –58, 52 (4) µm long, with 11 –15, 13 (4) and 13 –15, 14 (4) lateral teeth, respectively; inner spur 1.4–1.5 (4) times as long as outer spur; comb Ti III with 7 –8, 8 (4) bristles. Mid leg with 9 – 15, 11 (4) sensilla chaetica on apical 0.1 of ta 1, hind leg with 10 –15, 12 (4) sensilla chaetica on apical 0.1 of ta 1. Lengths and proportions of leg segments as in Table 2.
Genitalia (Fig. 3). Gp VIII triangular, rounded apically and produced in caudomesal position. Notum 110–130, 119 (4) µm long and 1.6–1.8 (4) times as long as rami. Csa nearly straight. Segment X without setae. Labia with microtrichia. Seminal capsule ovoid, 65 (2) µm long, 50–53 (2) µm wide, darkened on oral half.
Pupa (n = 12). Body length 4.0– 4.9, 4.3 (11) mm.
Coloration. Exuviae generally brown. Thoracic horn pale brown. Each of abdominal tergites II–VIII darkened anteriorly.
Cephalothorax. Thorax rugose in dorsomesal position. Thoracic seta Dc 1 granulate, 27 –33, 30 (8) µm long, and 0.53–0.79 (6) times as long as Sa; Dc 2 7 –10, 8 (7) µm long, with 3 or 4 branches apically (Fig. 4). Thoracic horn (Fig. 5 a) elongate conical, 320–380, 341 µm long, 2.3–2.5 times as long as its broadest width, with simple points on surface. Plastron plate oval, concave distally, 70 –105, 84 µm long, 0.52–0.66 times as long as broad, occupying distal 0.21–0.28 of horn length, with 17 –28, 23 (11) ostia on apical margin and 2 lateral aeropyles on basal margin. Tracheae usually present, a short internal supporting rod occasionally visible (Fig. 5 b).
Abdomen. Scar on T.I slightly darkened, 85 –110, 96 (11) µm long, and 0.43–0.55 (11) times as long as tergite along median line. Shagreen consisting of simple spinules or serial rows of 2–5 spinules (Fig. 6). Spiniform D 1 arising from somewhat large tubercles on T.II–VII. D 2 and D 3 taeniate and apically hooked on T.IV–V and T.III–V, respectively and arising from small tubercles (Fig. 7). A.VII–IX as in Fig. 8, A.VII and VIII each with 5 LS-setae; LS 1 on A.VII located 0.34–0.41 from anterior margin, on A.VIII located 0.55–0.61. Anal lobe (A.IX) 545–697, 591 µm long, 2.6–3.1 times as long as broad, with anterior and posterior macrosetae located 0.27–0.31 and 0.34–0.38, respectively, from anterior margin; inner margin with 10 –14, 12 spinules; outer margin nearly straight. Male genital sac 0.37–0.40 (6) times as long as anal lobe.
FIGURES 9–17. Bilyjomyia parallela n. sp., larva. 9, Labral region, dorsal view; 10, arrangement of ventral cephalic setae (S 9, S 10), submental seta (SS m) and ventral pore (VP); 11, apex of antenna; 12, maxillary palp with apical stylets; 13, mandible; 14, dorsomental plate; 15, ligula and paraligula; 16, pecten hypopharyngis; 17, smaller claws of posterior parapod.
Fourth instar larva (n = 1).
Coloration. Body red in alive specimen.
Head. Labral sclerite (Fig. 9) distinct, 0.36 times as broad as distance between cephalic S 2 -setae. Ventral cephalic seta S 9 simple, strong and 1.3 times as long as S 10 (Fig. 10). Antenna 1.2 times as long as mandible; lengths of segments 1–4 (µm) 203, 18, 5, 4; AR 6.2. Apex of antenna as in Fig. 11. A 1 5.8 times as long as basal width, with ring organ placed 0.73 from base; blade 25 µm long, reaching apex of A 3 and slightly shorter than accessory blade. A 2 3.5 times as long as wide, with style 13 µm long; peg sensilla 6 µm long. A 3 slightly longer than wide, and subtended by membranous stalk. Basal segment of maxillary palp (Fig. 12) 60 µm long, and 3.4 times as long as basal width; ring organ located 0.25 from base. Mandible (Fig. 13) 183 µm long, with basal tooth appressed and apically bifid; all ventrolateral setae simple. Dorsomental plate with 1 small and 6 large teeth (Fig. 14). Mappendage with pseudoradula granulated in distal half. Ligula (Fig. 15) 85 µm long, 1.4 times as long as its maximum toothed width, with basal granulose area reaching 0.12 of its total length; toothed margin deeply concave; median tooth 1.6 times as long as wide; inner laterals pointed forward; outer laterals 1.8 times as long as wide. Paraligula 43 µm long, bifid, with fork located 0.65 from base; outer tooth 2.3 times as long as inner tooth. Pecten hypopharyngis (Fig. 16) with 1 broadened mesal tooth, followed by row of 9 simple teeth becoming longer towards middle and 4 small points.
Body. Procercus 4.3 times as long as wide; both lateral setae located 0.38 and 0.83 from base, respectively. Smaller claws on posterior parapod with tooth depressed and expanded basally (Fig. 17).
Remarks. At present the genus Bilyjomyia includes three species: B. algens, B. fontana and B. parallela. Bilyjomyia parallela can be separated by the following features: (1) adult male: the wing has two dark bands against a single band observed in the other two species (Roback 1971, Niitsuma & Watson 2009), the tarsal claw is not accompanied by distinct pulvilli; (2) pupa: the thoracic horn has only two aeropyles against three in the other two species (Niitsuma & Watson l.c.), the abdominal tergite III possesses hair-like D 2 -setae, while taeniate setae are observed in the other two species (Roback 1984, Niitsuma & Watson l.c.); (3) larva: the labral sclerite is relatively large compared to the ones present in the other two species (Watson 1998, Niitsuma & Watson l.c.), the cephalic seta S 9 and the mandibular ventrolateral setae 2 and 3 are simple, while they are all branched in the other two species.
Ecology. The larvae of B. parallela were collected from the muddy bottoms of two springs in Shizuoka and Fukushima Prefectures, Japan, where are cool (15 – 16 and 13 – 15 °C, respectively, in summer) and slow streams flowing through dozens of meters. The larvae inhibit around the gushing points of the springs. The adults were captured in spring and autumn. The larvae of all the three known species are cold-stenothermal.