Asionurus primus Braasch & Soldán, 1986

Braasch, Dietrich & Boonsoong, Boonsatien, 2010, A contribution to the Heptageniidae (Insecta, Ephemeroptera) of Thailand and Malaysia, Zootaxa 2610, pp. 1-26 : 5-7

Asionurus primus Braasch & Soldán, 1986

First description of male imago. Body length 4.4–7.0 mm, forewing 6.0– 7.7 mm, hind wing 1.2–1.7 mm, caudal filaments 15.4 mm.

Head: Head yellow, compound eyes dark, contiguous dorsally; scapes and pedicels of antennae yellow, flagellae pale.

Thorax: Forewings transparent except C and Sc cells being semihyaline. Forelegs: femora with red pigmentation, length 1.7 mm, tibiae length 1.7 mm, tarsi length 2.3 mm, length of tarsal segments in descending order: 2>3=1>4>5. Midlegs: femora length 1.8 mm, tibiae length 1.4 mm, tarsi length 0.9 mm, lengths of tarsal segments in descending order: 1>5>2>3>4. Hind legs: length of femora 1.8 mm, tibiae length 1.4 mm, tarsi length 0.9 mm, lengths of tarsal segments in descending order: 1>2>5>3>4. Claws of all legs with a blunt, pad-like and a hooked portion.

Abdomen: General colour of abdomen reddish brown, terga IV–VII with striking median band of 4 dark brown lines of which oblique outer lines converge to vertical inner lines at distal margins of terga (Fig. 14). Genitalia: Posterior margin of subgenital plate convex, combined segment 3 and 4 of forceps 1/ 3x segment 2 (Fig. 15), penis lobes go apically close together, and titillators are sharply pointed, lobal halves are smoothly notched apically. (Figs. 16–17). Cerci whitish.

First description of female imago. Body length 7.0– 7.8 mm.

Thorax: Forewing 8.3 mm, hind wing 1.9 mm. Forelegs: femora 1.2x of tibiae, tarsi length 2.5 mm, lengths of foretarsal segments in descending order: 2>3>1>5>4. Midlegs: femora 1.2x of tibiae, tarsi length 1.0 mm, lengths of tarsal segments in descending order: 1>2>5>3>4. Hind legs: femora 1.1x of tibiae, tarsi length 1.0 mm, lengths of tarsal segments in descending order 1>5>2>3>4.

Abdomen: Colour pattern is alike that of male. Posterior margin of anal plate distally more rounded (Fig. 18).

PLATE III. FIGURES 14–18. Imagos of Asionurus primus Braasch and Soldán, 1986 14, Male, abdominal terga, color pattern. 15, Male genitalia, ventral view. 16, Penis, ventral view. 17, Penis, dorsal view. 18, Female, terminal part of sterna.

Diagnosis: Whereas in male of Asionurus primus the terga IV–VII are provided with a pair of paramedian straight stripes, in A. petersi Braasch & Soldán, 1986 stripes stand narrower bulging outwards at midlength. In the first species, lobal halves of penis are smoothly notched apically and titillators look bluntly pointed, whereas in A. petersi penis lobes go close together apically and titillators are sharply pointed. Female of A. primus has an anal plate more rounded distally (Fig. 18), that of A. petersi is pointed ( Braasch 2005: p. 169, Figs. 16–17).

Discussion. Sangpradub et al. (2002: p. 414, Fig. 2.2 a–g) found and illustrated larval specimens of genus Asionurus Braasch & Soldan, 1986 in northeastern Thailand, looking very like those in original description of A. primus from Vietnam. Now, we have examined a mature Thai male larva having approximately the prospective penis as shown by Braasch and Soldán (1986a: p. 158, Fig. 13) for A. primus . In the meantime, several adult females of this form have been collected in northern Thailand at light. Furthermore, we obtained a Vietnamese female of Asionurus (collected by W. Mey, Berlin, Germany) from the vicinity of locus typicus of A. primus in Vietnam, that matches completely those of northern Thailand. In spite of that, the status of A. primus and A. petersi should be paid further attention in future. The species spectrum of Asionurus is badly known at present. Even though, Braasch and Soldán (1986a) pointed out differences between larvae of some localities in Vietnam, only male larva provides at last fairly reliable details for species description.

Material examined: 1 male (reared), Northeastern Thailand, Chaiyaphum, Khon San, Phrom Laeng stream, 16°38’ N, 101°34’ E, alt. 720 m, 9.I.01; 2 SI females: North Thailand, Mae Hong Son Province, Soppong, Nam Lang River, 19°31’01.72’’ N, 98°14’53.79’’ E, alt. 605 m, at light, 02.II.–01.VI.05 (DB); 1 La, same locality, 02.II.–01.VI.05, bottom sample (DB); 5 La, same locality and same time, bottom samples (DB); ca 20 La, Thailand, Nam Rhin, small streams at upper slopes, 19°28’07.28’’ N, 98°17’42.82’’ E, alt. 829 m, 11.IV.03, bottom samples (DB); ca 12 La, Nam Rhin, small affluent of Nam Lang, pool-stream, same time, bottom samples (DB); 1 female, 4 La, North Thailand, Mae Hong Son Province, Nam Rhin, small stream, 17.II.04, at light and bottom sample (DB); 1 female, same locality, 30.III.07, at vegetation (DK); 10 La, same locality, 11.IV.03, bottom samples (DB); 2 SI females, Nam Rhin, small stream, 19.VI.05, at light (DK); 16 La, North Thailand, Mae Hong Son Province, near Mae Hung, a small stream to border of Myanmar, 19°41’44.42’’ N, 98°10’24.58’’ E, alt. 764 m, 23.II.04, bottom samples (DB); 6 La, North Thailand, Chiang Mai Province, Doi Suthep National Park, 18°48’20.05’’ N, 98°55’17.01’’ E, alt. 844 m, 03.–05.VI.05, bottom samples (DB); 1 SI female, 1 male La, North Thailand, same locality, near Chiang Mai, torrent, 03.– 05.VI.2005, at light, bottom sample (DB & DK).