Epeorus bifurcatus Braasch & Soldán, 1979

Braasch, Dietrich & Boonsoong, Boonsatien, 2010, A contribution to the Heptageniidae (Insecta, Ephemeroptera) of Thailand and Malaysia, Zootaxa 2610, pp. 1-26 : 23

Epeorus bifurcatus Braasch & Soldán, 1979

Material examined. 1 La: Thailand, Tak Province, 16°30’ N, 99°00’ E, alt. ca 400 m, XI. 2008, leg. Freitag, Manila, det. Braasch).

Diagnosis. Epeorus bifurcatus is a smaller species (length to 12 mm), recognizable by a pair of relatively short submedian spines on terga I–IX, flatly elliptical head ( Nguyen & Bae, 2004a: p. 21, Figs. 7,9), posterior margins of terga with densely rowed blunt bristles, surface of terga with very fine scattered setae, only a weak fringe of small setae shorter than spines in the medial groove of terga and with triangular gill I of same length as following gills, all equally ovaloid, and femora with spot ( Braasch & Soldán 1979: p.266, Figs. 15–22). Contrastingly, E. rhithralis , as well as E. bifurcatus , have ovaloid shape of head, long elliptic form of first gill, pointed bristles on posterior margins of terga and lack of groove on terga ( Braasch 1980: p. 63, Figs. 4 b–l). Other species from the region are either without any spines as Epeorus hieroglyphicus , E. khayengensis , E. papillatus , E. suspicatus , E. tiberius Braasch & Soldán, 1984 , or provided with pairs of tubercles like E. rhithralis or with pairs of long spines like E. aculeatus , E. bispinosus Braasch, 1980 and Iron martensi .

Discussion. Epeorus bifurcatus is new for Thailand. To date this species is only known from Vietnam ( Nguyen & Bae 2004a) and Thailand. Comments on its distribution are seen above under Epeorus inthanonensis . Adults and subadults are unknown.