Contribution to the genus Clypeocaenis Soldán, 1978 (Ephemeroptera: Caenidae) from Lao People’s Democratic Republic with a key to Oriental species Author Vannachak, Viengkhone Department of Biology, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand Author Malzacher, Peter Friedrich-Ebert-Strasse 63, 71638 Ludwigsburg, Germany Author Sangpradub, Narumon Department of Biology, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand & Center of Excellence in Biodiversity, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand text Zootaxa 2024 2024-09-03 5501 4 501 523 http://dx.doi.org/10.11646/zootaxa.5501.4.1 journal article 10.11646/zootaxa.5501.4.1 1175-5326 13745355 29E9284E-6F5C-46E5-BA25-B54F820BE0C0 Key to the larvae of Oriental Clypeocaenis species 1 Clypeal protrusion with 4 or more setae.................................................................... 2 – Clypeal protrusion with two setae........................................................................ 4 2 Clypeal protrusions with 20–35 long setae.These setae, along with those on the body surface, often possess many thin, irregularly arranged, and matted branches, creating what are referred to as sausage-shaped setae ( Malzacher 2013 , Figs. 37–39).................................................................................................. Cl. soldani – Clypeal protrusion with less than 20 long setae. Surface without sausage-shaped bristles, but with shield-shaped microtrichia ( Fig. 9A, C ).......................................................................................... 3 3 Clypeal protrusions with 10–15 long setae ( Fig. 9A ). The cuticle features shield-shaped, spider web-like microtrichia with smooth margins ( Fig. 8C ).................................................................... Cl. multisetosa – Clypeal protrusion with about 4 long setae and several short ones ( Fig. 6A ). Shield-shaped microtrichia with frayed margin ( Fig. 8A )................................................................................. Cl. oligosetosa 4 Mid and hind femora with long, acute marginal setae ( Soldán 1978 , Figs. 9 , 10 , 21). Operculate gill’s length more than twice its width, with blunt or spatulate marginal setae ( Balasubramanian & Muthukatturaja 2021 , Fig. 31).................... 5 – Mid and hind femora with short marginal setae ( Fig. 3D, E ). Operculate gill with very short length not more than 2 time as width, blunt or spatulate marginal setae, on lateral margin very short or absent ( Balasubramanian & Muthukatturaja 2021 , Fig.14 )............................................................................................. 8 5 Fore tarsus and the distance between the transverse rows of bases of filtering setae on the foretibia are of equal length ( Soldán & Landa 1991 , Fig. 14 )................................................................... Cl. femorisetosa – Fore tarsus 1.7 to 2 times as long as the distance between the transverse rows of bases of filtering setae on the foretibia ( Soldán 1983 , Fig. 12 )........................................................................................ 6 6 Genae margin angled. Foreleg with feathered bristles in some places, e.g. marginal on coxae and femora ( Muthukatturaja et al . 2020 , Fig. 27).............................................................................. Cl. sharadhae – Genae differently shaped. Fore leg without feathered bristles................................................... 7 7 Apical margins of the clypeal protrusion straight ( Soldán 1978 , Fig. 16). The third segment of the labial palp hardly widened basally ( Soldán 1978 , Fig. 3 ).................................................................... Cl. bisetosa – Apical margin of the clypeal protrusion rounded. The third segment of the labial palp significantly widened basally ( Balasubramanian & Muthukatturaja 2021 , Figs. 2 , 26).............................................. Cl. napoklu 8 Clypeal protrusions markedly large, apically domed. Genae protruding, doubly angled, the margin between angles straight ( Srinivasan et al . 2022 , Fig. 2A ).............................................................. Cl. malzacheri – Clypeal protrusion flatly rounded, not domed apically........................................................ 9 9 Setae of transverse row on forefemur broad ( Fig. 3A, B ). Segment I of maxillary palp narrow, about half as wide as galea-lacinia ( Fig. 2D ). Setae on outer margin of mid and hind femora spatulate, with a very thin basal part ( Fig. 3E, G ). Claws of mid and hind legs with 3–5 denticles ( Fig. 3F, H ). Ventral side of operculate gill without microtrichia ( Figs. 4G , 12F )............................................................................................. Cl. laosensis sp.nov. – Setae of transverse row on forefemur narrow. Segment I of maxillary palp broadened, about as wide as galea-lacinia. Setae on outer margin of mid and hind femora thin, acute or bifid. Claws of mid and hind legs with 8–10 denticles ( Balasubramanian & Muthukatturaja 2021 , Figs. 7 , 10–12 ;). Ventral side of operculate gill with a sublateral band of microtrichia ( Fig. 10D ).... 10 10 Pedicel two and a half time as long as third antennal segment; the latter about as long as the following segments; genae flatly angled. Segment III of labial palp basally strongly broadened Coxae enlarged, two third as wide as length of fore femur. Median ridge of operculate gill scarcely keeled ( Muthukatturaja et al . 2020 , Figs. 1 , 7–10 , 14 )...................... Cl. gayathri – Pedicel one and a half times as long as the third antennal segment; the latter distinctly longer than the following segments; genae margin not angled. Segment III of the labial palps not strongly broadened basally ( Balasubramanian & Muthukatturaja 2021 , Fig. 9 ). Coxa half as wide as the length of the forefemur. The median ridge of the operculate gill strongly keeled ( Balasubramanian & Muthukatturaja 2021 , Figs. 1 , 10–12 , 14 ).......................................... Cl. kaveri