Thalerosphyrus sinuosus Navas , 1933

Boonsoong, Boonsatien & Braasch, Dietrich, 2013, Heptageniidae (Insecta, Ephemeroptera) of Thailand, ZooKeys 272, pp. 61-93 : 72-74

Thalerosphyrus sinuosus Navas, 1933 Figs 3 B–D6C–D 9F

Thalerosphyrus sinuosus Navás, 1933: 70, F, Fig. 80. (orig.)

Larva.

Braasch and Soldán 1984b: 203-205 (sub name Thalerosphyrus siamensis Dang, 1967, Figs 5-20v, 26)

Adult.

Navás 1933: 70, F, fig. 80; Ulmer 1939: 551-555, M&F, Figs 118-128; Braasch and Soldán 1984b: 201-206, Figs 1-8, M, 25.

Eggs.

KCTs randomly scattered laterally and concentrated at both poles, although larger and numerous at the pole (Fig. 6C). Rounded tubercles are scattered all over the surface of the chorion (Fig. 6D). Five - six micropyles located on equatorial plane.

Distribution.

Widely distributed in many parts of Thai streams.

Diagnosis.

The combination of having a distinctly thickened anterior margin of the head capsule, long posterolateral spines on the abdomen, acutely pointed supracoxal spurs, and well-developed lamellae on gills 1 will distinguish Thalerosphyrus from other Ecdyonurinae genera. Within Thalerosphyrus is a ‘sinuosus’ group of species with larvae having the above-mentioned combination, having in both sexes of adults "costal and subcostal fields with two indistict umbra-brown spots, the first at the beginning of pterostigmatic region, the second directly to the wing tip" ( Navás 1933) and a ‘determinatus’ group, having larvae with short posterolateral spines; however, both sexes of adults have umbra-brown tinged costal and subcostal fields on forewings. In general, the species differentiation in the genus ( Thalerosphyrus ‘sinuosus’ group) is unsatisfying and requires verification. The larva of Thalerosphyrus sinuosus can be differentiated by the combination of the following characters: gill 3 of rounded shape is much less wide than that of Thalerosphyrus vietnamensis (Dang, 1967) and while in Thalerosphyrus flowersi ( Venkataraman and Sivaramakrishnan 1987) the inner side of gill 1 has a straight margin, that of Thalerosphyrus vietnamensis (= Thalerosphyrus sinuosus ?) is slightly concave.

Habitat and biology.

Thalerosphyrus sinuosus larvae (Fig. 9F) are one of the most widespread mayfly species in Thailand. The larvae are found underneath stones in slow-flowing reaches of streams (water velocity approximately 3-7 cm/sec, water depth ranges between 7-17 cm). The larvae cling to submerged boulders and cobbles. Because they feed by grazing on diatoms, algae and detritus on stream rocks, they prefer rocky substrates in fairly clear to silty sediments.

Remarks.

Only one species of Thalerosphyrus ( Thalerosphyrus sinuosus ) was identified from Thailand and this species widely distributed in Thai streams. The larva and adults of this species were adequately described by Braasch and Soldán (1984b) and Navás (1933).