Epeorus inthanonensis Braasch and Boonsoong

Braasch, Dietrich & Boonsoong, Boonsatien, 2010, A contribution to the Heptageniidae (Insecta, Ephemeroptera) of Thailand and Malaysia, Zootaxa 2610, pp. 1-26 : 17-19

Epeorus inthanonensis Braasch and Boonsoong sp. nov.

Description. HOLOTYPE: female La: Body length 9.3 mm, caudal filaments 13.0 mm; (Body length of male La 8.8 mm, caudal filaments 10.2 mm).

PLATE XI. FIGURES 69–74. Larva of Epeorus inthanonensis sp. nov. 69, Head capsule. 70, Labrum, dorsal view (left) and ventral view (right). 71, Right mandible. 72, Left maxilla, ventral view. 73, Hypopharynx, dorsal view (left) and ventral view (right). 74, Labium, dorsal view (left) and ventral view (right).

PLATE XII. FIGURES 75–82. Larva of Epeorus inthanonensis sp. nov. 75, Foreleg, right, dorsal view. 76, Foreleg femur, bristles on dorsal face. 77, Foreleg, tarsal claw. 78, Abdominal tergum VII, posterior margin. 79, Abdominal terga I–X. 80, Gill I. 81, Gill V. 82, Gill VII.

Head (Fig. 69): ellipsoid, width 10.2 mm, without conspicuous markings, but dark brown around ocelli, eyes and antennae sockets, light brown in rest area; antennae very long: 8.3 mm; HI 34:27 = 1.2. Labrum (Fig. 70): with median notch on anterior margin, with long hairlike setae dorsally and marginally. Mandibles (Fig. 71): lateral margin without setae, incisors weakly serrate; outer incisor longer than inner incisor. Maxillae (Fig. 72): with 3 acute teeth, medially with row of hairlike setae, apical segment of maxillary palp with dense, long, hairlike setae. Hypopharynx (Fig. 73): lingua with anterolateral lobes, superlinguae slightly expanded laterally with row of hairlike setae. Labium (Fig. 74): with narrow basal separation between glossae, glossae subtriangular, paraglossae slightly expanded laterally, apical segment of labial palp with heavy armature.

Thorax: Pronotum light brown without clear marks; mesonotum somewhat darker brown with each a paramedian pair of darker spots anteriorly and a pair of inside curved streaks posteriorly. Femora yellowbrown without distinctively visible patches, dorsally with median spot (Fig. 75), dorsal surface of femora with scattered stout short bristles (Fig. 76), claws with 2 small denticles (Fig. 77).

Abdomen: Prospective figures of adult stage is suggested by pigmentation of terga (Fig. 79); sterna light without any markings. Microstructure of terga characteristic as in segment VI (Fig. 78); along midline of terga II–VII a pair of small pointed tubercles; hind margins of terga with blunt bristles (Fig. 78). Gill plates I, III and VII as in Figs. 80–82.

Etymology: Denomination refers to collection site on the highest mountain of Thailand: Doi Inthanon.

Diagnosis: The new species most resembles Nepalese Epeorus rhithralis Braasch, 1980 and somewhat less Epeorus bifurcatus Braasch & Soldán, 1979 . The latter is best distinguished by small submedian, acute pairs of dorsal spines and larger gills I than gill III ( Nguyen & Bae 2004a); in the new species the first gill is, with exception of the seventh gill, smaller than gills II–VI, while in E. rhithralis the first gill is much larger than all other gills. Further differences can be seen in shape of head, hypopharynx, gill set, femur spot and posterior margin of tergum VII ( Braasch 1980: p. 63, Figs. 4 b; h; j; k; l; e and d). E. rhithralis as well as E. inthanonensis have paired tubercles on terga more rounded than in E. bifurcatus . E. inthanonensis has relatively the smallest first gill. In Vietnam specimens of E. bifurcatus , the hind margins of terga show blunt bristles densely rowed, whereas those of the two other species are pointed. E. inthanonensis has pairs of rounded, submedian tubercles on terga III–IX, densely provided with small conical bristles, forming a median groove between them, moderately scattered with tiny setae; obliquely running rim of the groove bears scarcely little setae directed mediodistally. The Hong Kong species Epeorus sagittatus Tong & Dudgeon, 2003 has, deviating from other Epeorus species of the region, the terga III–VIII each with a pair of rounded brown stripes submedially.

Discussion. The new species is among those derived from Himalayan species, having spread southeastward by following foothills of the Himalayas to Thailand, including species such as Epeorus (Belovius) unicornutus , Epeorus bifurcatus , or still other species of Epeorini Wang and McCafferty, 2004. In contrast to these obviously unchanged species with large geographic ranges between Nepal and Thailand or even Vietnam, E. inthanonensis seems to be a close related species to Nepalese E. rhithralis with a large first gill, while it is strongly reduced in E. inthanonensis .

Material examined: HOLOTYPE: female La, NW Thailand, Chiangmai Province, small mountain stream of Doi Inthanon, 18º31'33.35"N, 98º29'57.20"E, alt.> 2200 m; 19.II.2004 (DB) in 70% alcohol; PARATYPES: 3 La from the same place (DB); 3 La, small river from mountain region near Pai, 19°28’07.28’’N, 98°17’42.82’’E, alt. 829 m; 11.IV.03 (DB). All findings are bottom samples.

Types deposition: HOLOTYPE: female La; PARATYPES: 1 La ( MNHU), 2 La ( SMF Eph); 2 La ( ZMKU); 1 La (DBP).