Rhithrogeniella tonkinensis Soldan & Braasch, 1986

Boonsoong, Boonsatien & Braasch, Dietrich, 2013, Heptageniidae (Insecta, Ephemeroptera) of Thailand, ZooKeys 272, pp. 61-93 : 80

Rhithrogeniella tonkinensis Soldan & Braasch, 1986 Figs 4C8 A–B 9E

Rhithrogeniella tonkinensis Soldán & Braasch, 1986: 203-210, Figs 1-18. (orig.)

Larva.

Soldán and Braasch 1986: 203-210, Figs 1-18.

Adult.

Soldán and Braasch 1986: 203 (F), 206, 210 (Ms, Figs 19-22); Braasch 1990: 11-12, M, Figs 17.1-17.4.

Eggs.

Egg ovoid, chorionic surface with mesh-like reticular ridges of a hexagonal structure, evenly covered with KCTs (Fig. 8A), micropyle slightly oval with inconspicuous marginal rim, 1-2 small micropyles visible on the equatorial area (Fig. 8B).

Distribution.

Chiang Mai province, Chaiyaphum province.

Diagnosis.

The larvae of Rhithrogena tonkinensis can be distinguished from those of other genera of Heptageniidae by the following combination of characters: the head is approximately as broad as the pronotum, without a median emargination and marginal bristles and by the presence of interfacing setae on the caudal filaments ( Soldán and Braasch 1986). The latter are provided at rings with rather stout spines regularly alternating with fine setae. Segments of filaments are “scaled”. Larvae of the other Southeast Asian species Rhithrogeniella ornata Ulmer, 1939 are unknown.

Habitat and biology.

Larvae of Rhithrogena tonkinensis (Fig. 9E) occur in relative deep waters (30-40 cm) with slow currents and smaller stones or coarse sand on the bottom. Larvae are good swimmers, but prefer to remain attached to the stone surface rather than swimming ( Soldán and Braasch 1986).

Remarks.

The larva and adults of Rhithrogena tonkinensis were adequately described by Soldán and Braasch (1986). Only Rhithrogena tonkinensis found in relative deep waters with slow currents of Thai streams.