Chironomus okinawanus Hasegawa & Sasa, 1987.

Synonyms:

Adults

Males (From Sasa & Hasegawa 1983):
Wing length 2.81 (2.50-3.01), setae on squamal fringe 15 (13-20); AR 3.28 (3.07-3.51).
Setae: Clypeal 20.3 (16-23); Acrostichal 19.1 (16-23); Dorsocentral 17.8 (15-24); Prealar 7.9 (6-11); Scutellar 19.3 (16-23).
LRI 1.53 (1.49-1.56); LR2 0.64 (0.62-0.66; LR3 0.75 (0.73-0.78); BR 12.5 (2.3-2.6).
Antennal hairs brown, shaft dark brown; ground color of scutum yellow, scutal stripes reddish brown, scutellum yellow, postnotum dark brown, halteres yellow; wings unmarked, r-m dark brown; in all legs, femur and tibia are entirely yellow, tarsi I, II and III largely yellow and each with an apical dark ring, tarsi IV and V largely dark brown; ground color of abdominal targites greenish yellow, tergites I to VII each with a large central dark patch which is almost triangular in tergites II to IV (Fig. below); tergites VIII and hypopygium dark brown.  Frontal tubercles well developed, about twice as long as wide.  Lateral pronotal setae absent.  Hypopygium (see Fig. 1, below). Ninth tergite with 12-16 long setae in the middle.  Anal point slender and slightly expanded apically.  Superior Volsella (Fig. I below) composed of a relatively high, triangular base bearing several long setae, and a hook-like apical process.  Inferior Volsella (Fig. 1, below) relatively short, stout and almost parallel-sided, with 14 long and recurved setae arising from apical 1/5.  Gonostylus abruptly narrowed at about apical 1 /3.

Male hypopygium (left) and abdominal tergites (right) of C. okinawanus
From Sasa & Hasegawa 1983.

Female (From Sasa & Hasegawa 1983):
Coloration as in male, presence of a large dark patch on each of abdominal tergites I to VI is also a differentiating character of this species in female.  Frontal tubercles prominent, widest at base and tapering, 54 µm long and 18 µm diameter, 48 µm apart from each other.  Antenna 6 segmented, segments II to V each with a long neck, last segment with long and curved sensory setae.  Spermathecae faint in contour 100 µm long and 74 µm wide in one, 90 µm long and 82 µm wide in another.  Cercus roughly rhombic, 176 µm high and 120 µm long.

Fourth instar larva: (Fig. 2: D-5 to 13, at right).  (Apparently a melanotus-type larva).
Body 8.8 to 13.2 (mean 11.l) mm long, red in color.  Two pairs of eyes present.
Head structure closely resembles that of C. javanus.  Relative length of antennal segments, 47: 12: 3: 3: 2: AR about 2.35; ring organ in proximal 1/3 of basal segment of antenna.  Anterior and posterior pseudopods as in C. javanus.
Abdominal segment VII with a pair of caudolateral tubules reaching middle of abdominal segment VIII.  Two pairs of simple and straight blood gills present on abdominal segment VIII, the anterior pair longer.  Preanal hair tuft composed of 7 long and 2 short minute hairs on small tubercle.  Anal gills slender, almost the same in length.

Cytology:  Not known.

Hasegawa & Sasa (1987) note that the adult is closest to C. praeapicalis Tokunaga (1964); while the pupa is similar to C. circumdatus in having a pair of spinulous areas in place of transverse band of spinules on the anterior part of tergite VII, but differs in possesing spinulous areas on the antero-lateral corners of sternite I. Yamamoto (2002) has suggested that this species is related to C. javanus (or should that be C. vitellinus?) and aspects of the description suggest it is most closely related to C. javanus or C. vitellinus (perhaps a color variant?).

Found: Japan - Type locality - Okinawa, Okinawa Prefecture, Ryukyus.(In Toyama Medical and Pharmaceutical University, Toyama, Japan);
           Shinri Beach, Kume Island (26.35°N, 126.70°E), Okinawa Prefecture.
           Thailand - 23. Tambon Talad (16.33°N, 103.49°E), Mueang Maha Sarakham District, Maha Sarakham Province.