Material examined

Holotype, ♂ larva (on microslide): SKP 1.2, Thailand, Nakhon Phanom Prov., Tat Kham Waterfall, 17°57′03.65″N, 104°09′13.30″E, 190m, 20.03.2012, N. Sangpradub leg., SMNS_ EPH_007784_M. – Paratype, 1 ♂ larva, same data as holotype.

Etymology

The species is dedicated to my third grandchild Ludovico.

Male subimago

The holotype is a last instar male larva. The following subimaginal features are therefore visible and can be described:

Base of antennal flagellum dilated, dilated part half as wide and about three fourth as long as pedicel. Prosternal ridges forming a narrow trapezoid with straight or slightly concave lateral sides. Segments 2 and 3 of fore tarsus each with a long apico-median projection, segment 4 with two projections, a lateral and a median one (Fig. 1c). Scutellum very broad. Abdominal segments with very short posterolateral processes. Sternite IX and subimaginal genitalia as in Fig. 1a. Penis narrow, postero-laterally broadly rounded, ventrally with 4–5 parallel folds forming a V. Forcipes straight and very broad, with a strong, stepped apical spine (Fig.1b).

Larva

Measurements and colouration

Male larva of last instar, body length 3.8 mm, length of cerci 2.5 mm.

Colouration of cuticle light yellowish-brown to yellowish. Epidermal pigmentation: Traces of pigments on vertex, pronotum and abdominal terga. Pronotum with two paramedian spots. Operculate gills brownish.

Morphology

Cuticle: surface scattered with long or very long, thin hair-like bristles, particularly on marginal parts of body, on wing buds and on operculate gills; most of these bristles are erected, body therefore seems to have a halo of hairs.

Head: Genae not bulging out. Mandibles dorsolaterally with numerous moderate bristles. Labial palp besides the marginal strong spines laterally with numerous long hair-like bristles. Similar bristles scattered on prementum. Ratios of maxillary and labial palps and their segments see Table 1.

Thorax: Sides of pronotum convex and slightly diverging anteriorly, with about 12 long bristles, between them short, more or less spatulate ones. Sides of mesonotum with an anterior-lateral nose-shaped projection provided with long bristles (Fig. 1e). Coxal processes inconspicuous. Forefemur on dorsal side with a dense transverse row of about 10 (7 + 3) long, spatulate bristles (Fig. 1d); similar, but longer bristles on margin apically from the transverse row, together with few very long pointed bristles. Mid and hind femora marginally and basally on dorsal side with very long, hair-like bristles, apically with spatulate ones, a little narrower than those from the transverse row, a little stronger, long bristles on tibiae. Foretarsus ventrally with 3–4 very short and inconspicuous simple bristles. Mid and hind tarsus with a row of 5–6, somewhat longer bristles. Hind tarsus additionally with an apical pinnate bristle. Claws slender, slightly bowed, with few, small denticles.

Abdomen: Abdominal segments with posterolateral processes of moderate length; margins with long bristles, basally more or less broadened (Fig. 1a). Bristles of all segments (III–IX) of similar shape and length, about 12 on segment VII, about 7 on segment IX. Posteriomedian process of tergum II very short, broadly triangular. Hind margin of tergum VII–IX with very long, hair-like bristles, tergum X with small denticles. Hind margin of sternum IX medially cut or slightly concave, with long bristles, the median ones a little shorter and bent medially (Fig. 1a). Shagreen on dorsal side of sternite IX consisting of about 3 long irregular rows of denticles parallel to hind margin (Fig. 1a). Operculate gill with long or very long bristles on lateral and hind margin, bristles on inner margin shorter; dorsal surface with very long, erect bristles, the longest more than half as long as width of gill (Fig. 1f). Y-shaped ridges inconspicuous, posteriorly reduced, marked by rows of long bristles. Ventral row of microtrichia running relatively close to lateral margin ending in the middle of hind margin (Fig. 1f). Gill I more than half as long as gill II, with segment I a little elongated.

Differential Diagnosis

Caenis ludovici can be distinguished from all other Caenis species by the following combination of characters: Male: Base of antennal flagellum dilated. Segments 2 and 3 of foretarsus each with a long apico-median projection. Penis narrow, postero-laterally broadly rounded, ventrally with 4–5 parallel folds forming a V (Fig. 1a). Forcipes straight and very broad, with a strong, stepped apical spine (Fig.1b). Larva: Cuticle, particularly marginal parts of body, wing buds, and operculate gills scattered with long, erected hair-like bristles. Sides of pronotum with about 12 long bristles, between them with short, more or less spatulate ones. Sides of mesonotum with an anterior-lateral nose-shaped projection provided with long bristles (Fig. 1e). All claws basally with few small denticles. Hind margin of tergum VII–IX with very long hair-like bristles, tergum X with small denticles. Hind margin of sternum IX medially cut or slightly concave, with long bristles.

Material examined

Holotype, ♂ larva (microslide), CYP 3.2, Thailand, Chaiyaphum Prov., Huai Tat Fa, Phu Khiao Wildlife Sanctuary, 07.05.1996, SMNS_EPH_007785_M.

Paratypes: CYP 3.4, Thailand, Chaiyaphum Prov., Tat Fa Noi, Phu Khiao Wildlife Sanctuary, 07.02.1996, 1♀ larva. – CYP 3.5, Thailand, Chaiyaphum Prov., Huai Mai Sod Noi, Phu Khiao Wildlife Sanctuary, 15.11.1998, 3♂ larvae, 1♀ larva. – CYP 3.6, Thailand, Chaiyaphum Prov., Huai Mai Sod Yai, Phu Khiao Wildlife Sanctuary, 15.11.1998, 1♂ larva, 2♀ larvae.

Other material: PCB 5.3, Thailand, Petchabun Prov., Yakraue, Nam Nao National Park, 16° 44′ 21.60″N, 101° 34′ 28.84″E, 24.04.2002, 3♀ larvae. – PCB 5.6, Thailand, Petchabun Prov., Yakraue, Nam Nao National Park, 16° 44′ 21.60″N, 101° 34′ 28.84″E, 17.08.2014, 1♀ larva. – PCB 5.9, Thailand, Petchabun Prov., Yakraue, Nam Nao National Park, 16° 44′ 21.60″N, 101° 34′ 28.84″E, 24.04.2002, 3♂ larvae. – CYP 1.6, Thailand, Chaiyaphum Prov., Huai Tat Fah Noi, 16° 27′ 24.50″N, 101° 47′ 41.10″E, 28.03.2000, 1♀ larva. – SKK 1.1, Thailand, Sakon Nakhon Prov., Huai Ven Prai, 20.04.1998, 2♀ larvae. – LOI 3.1, Thailand, Loei Prov., Huai Wang Yow, 16° 58′ 94.20″N, 101° 46′ 60.50″E, 09.11.2002, 2♀ larvae. – SKP 1.2, Thailand, Nakhon Phanom Prov., Tat Kham Waterfall, 17° 57′ 03.65″N, 104° 09′ 13.30″E, 20.03.2012, 1♀ larva. – THW 1.1, Thailand, Loei Prov., Tad Hong Waterfall, Phu Kradueng National Park, 16° 48′ 11.60″N, 101°34′ 52.90″E, 09.12.2010, 3♀ larvae. – POG 2.6, Thailand, Loei Prov., Phong River, 16°50′ 50.20″N, 101°56′1 3.80″E, 23.02.2011, 1♂ larva. – all N. Sangpradub leg.

Etymology

The species epithet refers to to nose-shaped lateral projections on mesonotum, from Latin nasus, nose.

Male subimago

The holotype and some other specimens are male last instar larvae. The following subimaginal features are therefore visible:

Base of antennal flagellum dilated, dilated part 0.4 times as wide and about as long as pedicel. Prosternal ridges forming a very narrow trapezoid with concave lateral sides. Segments 2 and 3 of foretarsus each with a moderate apico-median projection, segment 4 with two projections, a lateral and a median one. Abdominal segments each with short triangular posterolateral process. Sternite IX and subimaginal genitalia as in Fig. 2a. Penis of moderate width, postero-laterally rounded, no ventral fold visible. Forcipes straight and of moderate length, apically with a tuft of thin sclerotized spines (Fig. 2d).

Larva

Measurements and colouration

Male larva of of last instar, body length 3.0–3.2 mm, length of cerci 1.7 mm. Female larva of last instar, body length 3.8 mm, length of cerci 3.0 mm.

Colouration of cuticle yellowish-brown. Epidermal pigmentation: Transverse stripe of brownish pigments between antennal bases, each a pair of paramedian spots on pro- and mesonotum together with diffuse marks. Abdominal terga I–II with brownish transverse bands, Terga VII–IX with broad median marks divided from paratergal dashes by pale spots. Operculate gills shaded brownish.

Morphology

Cuticle: with very small granules (head, pronotum) or denticles (mesonotum, operculate gill, median field of the latter with net meshes).

Head: Genae slightly bulged. Mandibles with a dorsolateral band of very thin bristles. Outer margin of segments 1 and 2 of labial palp with numerous strong bristles. Ratios of maxillary and labial palps and their parts see table 1.

Thorax: Sides of pronotum straight or slightly convex, anteriorly diverging, with small denticles, without setation. Sides of mesonotum with an anterior-lateral nose-shaped projection densely provided with short spatulate bristles (Fig. 2g). Coxal processes tongue-shaped, broadly rounded triangular, process of hind coxa longer than that of mid coxa (Fig. 2f). Forefemur on dorsal side with transverse row of conspicuous, broadly spatulate bristles (Figs 2e); somewhat longer bristles on hind margin apically from the transverse row. Mid and hind femora and tibiae marginally with moderate, blunt, or slightly spatulate bristles. On dorsal side scattered bristles shaped like bristles of transverse row. Foretarsus ventrally with 4–6 short, simple or slightly pinnate bristles. Mid tarsus with a row of about 7 bristles, apically pinnate, basally simple, and hind tarsus with an outer row of about 6–7 pinnate bristles and an inner row of about 6 simple and one apical pinnate bristle. Foreclaws slender, with 2–3 very small basal denticles, mid claw with about 5 small basal denticles, hind claw with a dense row of microdenticles or pins only, or additionally with one or two small basal denticles.

Abdomen: Abdominal segments with posterolateral processes of moderate length, on segment VIII and IX shorter; margins with 6–12 thin, densely arranged bristles, most of them long and pointed (Fig. 2c), segment VIII with about 3 bristles of moderate length and few very short ones (Fig. 2b), segment IX with only one or two short bristles or without (Fig. 2a). Dorsolateral group of bristles on tergum VII composed of 30–40 pinnate bristles, the lateral ones long and strongly pinnate. Tergum II with cone-shaped, erect posteriomedian process, hind margin laterally with rounded denticles. Hind margin of tergum VII with about 20–25 long bristles, tergum VIII with about 8–12 slightly shorter bristles, tergum IX and X with small rounded denticles. Hind margin of sternum IX rounded, with moderate, thin bristles, the median ones deeply bifurcated (Fig. 2a). Shagreen on dorsal side of sternite IX consisting of only 1 rows of very small denticles immediately on hind margin (Fig. 2a). Operculate gill (Fig. 2h) with moderate bristles on lateral margin and long ones on hind margin, about 12 short or very short spatulate bristles on posterior-lateral corner, bristles on inner margin moderate or short; dorsal surface without bristles. Y-shaped ridges flat, inner ridge anteriorly with 5 spatulate bristles of moderate length, posterior part reduced. Ventral row of microtrichia running close to lateral and posterior margin ending at the inner corner (Fig. 2h). Gill II about 2 times length of gill I.

Differential diagnosis

Caenis nasuta can be distinguished from all other Caenis species by the following combination of characters: Male: Base of antennal flagellum dilated. Prosternal ridges forming a very narrow trapezoid with concave lateral sides. Segments 2 and 3 of foretarsus each with a moderate, apico-median projection. Penis lobes broadly rounded (Fig. 2a). Forcipes straight and of moderate length, apically with a tuft of thin spines (Fig. 2d). Larva: Sides of mesonotum with an anterior-lateral, nose-shaped projection densely provided with short, spatulate bristles (Fig. 2g). Coxal processes tongue-shaped, with denticulated margins (Fig. 2f). Ventral row of microtrichia on operculate gill running close to lateral and posterior margin ending at the inner corner (Fig. 2h). Gill II about 2 times length of gill I.

Material examined

Holotype. ♂ larva (on microslide): CYP 3.4, Thailand, Chaiyaphum Prov., Tat Fa Noi, Phu Khiao Wildlife Sanctuary, 07.02.1996, SMNS_EPH_007786_M.

Paratype: CYP 3.10, Thailand, Chaiyaphum Prov., Nong Kog Koy stream, N 16° 06′ 46.00″, E 102° 00′ 01.31″, 31.08.2003, 1♂ larva.

Other material: PCB 3.3, Thailand, Petchabun Prov., Nam Nao National Park, 16°38′24.02″N, 101°34′52.90″E, 740 m, 09.04.2013, 1♂ larva. – SKP 1.3, Nakhon Phanom Prov., Tat Pho Waterfall, 17° 57′ 46.58″N, 104° 08′ 24.39″E, 23.09.2012, 1♀ larva. – SKK 1.4, Thailand, Sakon Nakhon Prov., Keng Mod Dang, Phu Phan National Park, 12.02.1998, 1♀ larva. PNG 90, Papua New Guinea, Gulf prov., Marawaka, Mala, 7°5′664S, 145°44′467E, 1400 m, 11.11.2006, Balke & Kinibel leg.–other material: PNG 171, Papua New Guinea, Central prov., Kokoda Trek, 9°14′339S, 147°40′538E, 01.2008, 1400 m, 2♀ larvae, Posman leg. [MZL]

Etymology

The species epithet refers to the very long forcipes.

Male subimago

The holotype is a male last instar larva. The following subimaginal features are therefore visible:

Base of antennal flagellum not dilated. Prosternal ridges anteriorly more or less parallel, forming a rectangle or trapezoid (Fig. 3c). Segments 2–4 of foretarsus apically each with two projections, a lateral and a median one. Abdominal segments with short posterolateral processes. Sternite IX and subimaginal genitalia as in Fig. 3a. Penis broad, anvil-shaped, no ventral fold visible. Forcipes very long, with parallel sides, apical third slightly bend medially, with a tuft of short sclerotized spines (Fig. 3b).

Larva

Measurements and colouration

Male last instar larva: body length 3.3–3.5 mm, length of cerci 2.3 mm. Female last instar larva: body length 5.0 mm, length of cerci 3.0 mm.

Colouration of cuticle yellowish to brown. Epidermal pigmentation: All specimens are last instar larvae with imaginal pigmentation visible below larval cuticle.

Morphology

Cuticle: inconspicuous, mesonotal nose and dorsal surface of femora and tibiae with small denticles.

Head: Genae scarcely bulged. Mandibles with a dorsolateral band of long, bowed bristles. Ratios of maxillary and labial palps and their parts see Table 1.

Thorax: Sides of pronotum straight or slightly convex, anteriorly diverging, with small denticles, without setation. Sides of mesonotum with an anterior-lateral nose-shaped projection without setation. Coxal processes inconspicuous. Forefemur on dorsal side with a transverse row of conspicuous, broadly spatulate bristles; slightly longer bristles on hind margin apically from the transverse row. Mid femora with long marginal bristles only apically on hind margin (Fig. 2i); hind femora with long, blunt or spatulate bristles on fore- and hind margin (Fig. 2j). Dorsal side of mid and hind femora with numerous bristles like those from transverse row, a little longer and narrower (Figs 2i and j). Foretarsus ventrally with 4 simple bristles. Mid tarsus with a row of about 6–7 bristles, the apical ones pinnate, the basal ones simple, and hind tarsus with an outer row of about 6 pinnate bristles and an inner row of about 6 simple bristles; both rows close together. Fore claw thin and slender, with about three small basal denticles (Fig. 3f); mid claw broader and bowed with about 5 small, basal denticles (Fig. 3g); hind claw with tip strongly bent and a dense row of microdenticles or pins, the apical ones clearly longer than the basal ones, without basal denticles (Fig. 3h).

Abdomen: Abdominal segments with posterolateral processes of moderate length, on segment VIII and IX shorter. Marginal setation sparser as in C nasuta. Segments VI and VII with 6–7 moderate or long bristles with short or elongated, thin tips; segment VIII with about 4 short or moderate, blunt or shortly pointed bristles; segment IX with 1–3 short, blunt bristles (Fig. 3a). Tergum II with a flat, triangular, erect posteriomedian process. Dorsolateral group of bristles on tergum VII composed of 15–20 relatively short, pinnate bristles, the longest half as long as the longest in C. nasuta. Hind margin of tergum VII with about 20 bristles, most of them long and pointed or apically hair-shaped, few of moderate length with a short tip and one or two apical ones short and spatulate. The row of about 6 moderate bristles on hind margin of tergum VIII with a median gap. Hind margin of tergum IX and X with small rounded denticles. Hind margin of sternum IX broadly rounded, with few thin bristles, the median ones bifurcated (Fig. 3a). Shagreen on dorsal side of sternite IX nearly invisible, sometimes few, very small denticles on hind margin. Operculate gill (Fig. 3d) with bristles of moderate length on lateral margin and long ones on hind margin, few short or moderately long, spatulate bristles on posterior-lateral corner, bristles on inner margin moderately long or short; bristles sparser than in C. nasuta. Y-shaped ridges strongly reduced, the inner ridge only represented by few bristles: anteriorly 4 short to moderate, spatulate bristles, posteriorly three long and thin ones (Fig. 3d). Ventral row of microtrichia a little more distant to the lateral margin as in C. nasuta, ending in the middle of hind margin (Fig. 3d). Microtrichia short, more or less rounded (Fig. 3e). Gill II about 1.4 times length of gill I.

Egg

Broadly oval. Chorion with very fine pores. Two coiled-rope epithemata of a modified perpusilla subtype (see Malzacher 2011, fig. 13, pp. 65 and 73); about 6–8 threads forming loops and ending in the same number of tiny elongated knobs. Micropyle of moderate length, without widened mouth and visible sperm-guide.

Differential diagnosis

Caenis longiforcipata can be distinguished from all other Caenis species by the following combination of characters: Male: Base of antennal flagellum not dilated. Prosternal ridges anteriorly more or less parallel, forming a rectangle or broad trapezoid (Fig. 3c). Segments 2–4 of foretarsus apically each with two projections, a lateral and a median one. Penis broad, anvil-shaped. Forcipes very long, with parallel sides, with a tuft of short sclerotized spines (Fig. 3b). Larva: Sides of mesonotum with an anterior-lateral nose-shaped projection without setation. Fore- and mid claws with few basal denticles, hind claw only with a long, dense row of microdenticles or pins (Fig. 3h). Shagreen on dorsal side of sternite IX nearly invisible, sometimes few very small denticles on hind margin. Y-shaped ridges of operculate gill strongly reduced, the inner one only represented by few bristles: anteriorly 4 short to moderate spatulate bristles, posteriorly three long and thin ones (Fig. 3d). Egg: Two coiled-rope epithemata of a modified perpusilla subtype.

Caenis ulmeriana group

Remarks: There are numerous similar larvae with variable characters. However, males of last instar show some differences in subimaginal genital structures. There are two differing types and a couple of intermediate stages. The genitalia of one type are very similar to the genitalia of Caenis ulmeriana, a species that is widely distributed in the eastern Oriental realm. Here we will describe this larval type as larva of Caenis ulmeriana, although it cannot be excluded that there are different species with very similar larvae.

Malzacher (2015: 33)

Material examined

PCB 7.1, Thailand, Petchabun Prov., Huai Mod, Nam Nao National Park, 16° 40′ 05.70″N, 101° 44′ 11.8″E, 20.07.2002, 4♂larvae, 1♀ larva. – CYP 1.6, Thailand, Chaiyaphum Prov., Huai Tat Fah Noi, 16° 27′ 24.50″N, 101° 47′ 41.10″E, 23.03.2000, 1♂larva. – NKK 1.3, Thailand, Nakhon Ratchasima Prov., Wang Tao Waterfall, Thap Lan National Park, 14° 20′ 12.13″N, 102° 14′ 33.69″E, 27.04.2014, 2♂ larvae. – THW 1.1, Thailand, Loei Prov., Tad Hong Waterfall, Phu Kradueng National Park, 16° 48′ 11.60″N, 101°34′ 52.90″E, 09.12.2010, 2♂ larvae, 3♀ larvae. – POG 1.8, Thailand, Maha Sarakham Prov., Ban Kui Pang, Phong River, 16° 23′ 31.70″N, 102°57′ 19.20″E, 24.12.2004, 2♂ larvae, 1♀ larva. – POG 2.2, Thailand, Khon Kaen Prov., Huai Bong, Phong River, 16° 57′ 32.40″N, 101° 49′ 04.00″E, 21.08.2002, 2♂larvae, 6♀ larvae. – POG 2.4, Thailand, Loei Prov., Huai Phong Go, Phong River, N 16° 52′ 00.49″, E 101° 52′ 11.10″, 23.02.2011, 5♂ larvae, 4♀ larvae. – POG 2.8, Thailand, Khon Kaen Prov., Ban Huaisai, Phong River, N 16° 46′ 20.30″, E 102° 38′ 03.50″, 23.02.2011, 1♂ larva, 1♀ larva. – POG 2.10, Thailand, Khon Kaen Prov., Ban Kut Kwang, Phong River, N 16° 42′ 16.70″, E 102° 49′ 29.40″, 24.02.2011, 1♂ larva, 2♀ larvae. – POG 3.2, Thailand, Khon Kaen Prov., Huai Sun, Phong River, N 16° 31′ 06.63″, E 102° 53′ 55.14″, 12.07.2013, 1♂ larva, 1♀ larva. – all N. Sangpradub leg.

Male subimago

Some specimens are male last instar larva. The following subimaginal features are therefore visible:

Base of antennal flagellum not dilated. Prosternal ridges forming an elongated, cone-shaped structure. Segments 2–4 of fore tarsus apically each with two projections, a lateral and a median one; projections on segments 2 and 3 rather long, on segment 4 short. Abdominal segments with short to moderate posterolateral processes. Sternite IX and subimaginal genitalia as in Fig. 4a. Penis broadly rounded, ventral fold medio-posteriorly protruding, forming a semicircular or semi-elliptical process. Forcipes moderate, straight, sides apically slightly converging, with a tuft of sclerotized spines, the longest clearly wider as the others (Fig. 4c). The above-mentioned differing type shows a penis without semicircular ventral fold (Fig. 4b) and forcipes with elongated apical spines (Fig. 4d).

Larva

Measurements and colouration

Male last instar larva: body length 2.7–3.2 mm. Female larva of last instar, body length 3.8–5.0 mm. Cerci not complete.

Colouration of cuticle yellowish brown. Epidermal pigmentation: brown pigments in a transverse band between lateral ocelli, with an oval or triangular mark behind frontal ocellus; two spots or star-like marks on vertex. Pronotum with a median anvil-shaped mark, laterally with irregular spots and dashed. Mesonotum with angled dark-brown dashes on anterolateral corners, few spots behind them. Visible abdominal terga with diffuse sublateral marks. Operculate gills slightly shaded.

Morphology

Cuticle: inconspicuous, operculate gill and dorsal surface of femora with small denticles, partly net-meshed.

Head: Genae slightly bulged. Pedicel with 3–4 strong and pointed bristles, the apical one often bifid. Mandibles with a dorsolateral row or band of strong, bowed bristles. Three to four long, strong, blunt bristles in front of the eyes. Ratios of maxillary and labial palps and their parts see Table 1.

Thorax: Sides of pronotum straight, more or less diverging anteriorly, smooth or with few small denticles, without setation. Sides of mesonotum without an anterior-lateral nose-shaped projection. Few thin bristles anteriorly from coxae. Coxal processes sickle-shaped. Forefemur on dorsal side with a transverse row of conspicuous, broadly spatulate bristles in two groups (4–6 anterior + 2–3 posterior); somewhat longer bristles on hind margin apically from the transverse row (Fig. 4g). Mid and hind femora with moderate or long marginal bristles. Dorsal side of mid femora with 5–6 irregularly arranged spatulate bristles (Fig. 4h), hind femora with 3–4 bristles. Foretarsus ventrally with 2–3 simple bristles. Mid tarsus with a row of about 5–6 simple bristles, the apical one often pinnate, hind tarsus with an inner row of 5–6 simple bristles and 1–2 pinnate bristle as a rest of the outer row. Foreclaw thin and slender, with 2–3 small basal denticles (Fig. 4i); mid claw broader and bowed with about 3 small basal denticles; hind claw with strongly bent tip, 2–3 basal denticles, and a dense row of microdenticles or pins, becoming shorter to the apical end of the row (Fig. 4j).

Abdomen: Abdominal segments with posterolateral processes of moderate length, on segment VIII and IX shorter. Segment VII with 7–9 short, moderate and long bristles, the short ones blunt, the moderate and longer ones pointed. Segment VIII with 5–7 short or moderate, blunt or shortly pointed bristles; segment IX with 3–5 short, blunt or pointed bristles (Fig. 4a). Tergum II with a broadly triangular posteriomedian process, hind margin with denticles. Dorsolateral group of bristles on tergum VII composed of about 15 moderate, thin pinnate bristles. Hind margin of tergum VII with about 18–25 bristles, moderate or long, apically more or less hair-shaped. The row of about 12–14 moderate bristles on hind margin of tergum VIII without median gap. Hind margin of tergum IX and X with small denticles. Hind margin of sternum IX broadly or triangularly rounded, sometimes posteriorly more or less cut, laterally with few moderate and thin bristles, medially with short bifurcated bristles (Fig. 4a). Tergum IX of females posteriorly more elongated. Dorsal side of sternite IX with more or less triangular shagreen field, consisting of irregular transverse rows of denticles. Operculate gill (Fig. 4f) with moderate or long bristles on lateral margin and long or very long ones on hind margin, between moderate or long bristles, on postero-lateral corner a few short, more or less spatulate bristles can be found (Within the ulmeriana group there are also gills with long marginal bristles only). All these bristles are basally broadened and apically strongly pointed, but of different length. The longest bristles have a hair-like appearance. Y-shaped ridges weakly developed, the inner one posteriorly reduced, with 5–6 spatulate bristles in the apical half or two third (Fig. 4f). Ventral row of microtrichia reaches more or less the posteromedial corner, becoming smaller and smaller towards the end of the row. Microtrichia short and rounded, sometimes a little elongated. Gill I about half as long as gill II. Gill III with moderate filaments, half of them with 3–4 branches (Fig. 5)

Egg

Broadly oval (Fig. 6). Chorion with fine pores and irregular, weakly developed net-meshes (Fig. 7b, 8). One epithema; initial stage flat, forming a coil of fine threads, ending in knobs of different size, surrounded by the coil (Fig. 7a). Later on, epithemata become more or less uncoiled (Fig. 6). Micropyle of moderate length, with a scarcely visible circular sperm-guide (Fig. 8).

Material examined

Holotype. ♂ larva (on microslide): CYP 1.5, Thailand, Chaiyaphum Prov., Huai Tat Fa Noi, N 16° 27′ 24.50″ E 101° 47′ 41.10″, 23.03.2000. SMNS_EPH_007787_M.

Paratypes. Same data as holotype, 1♀ larva. – CYP 1.2, Thailand, Chaiyaphum Prov., Huai Tat Fah Noi, 16° 27′ 24.50″N, 101° 47′ 41.10″E, 28.03.2000, 1♂ larva – CYP 1.6, Thailand, Chaiyaphum Prov., Huai Tat Fah Noi, 16° 27′ 24.50″N, 101° 47′ 41.10″E, 28.03.2000, 2♀ larvae. –CYP 1.8, Thailand, Chaiyaphum Prov., Huai Tat Fah Noi, 16° 27′ 24.50″N, 101° 47′ 41.10″E, 28.03.2000, 1♀ larva –

Other material: MUN 2.1, Thailand, Burirum Prov., Tha Sai Ban Wang Plad, Mun River, 15° 26′ 04.00″N, 103° 00′ 49.90″E, 23.02.2003, 1♀ larva. – LAO 1.1, Laos, Nam Tou, N 18° 54′ 00.01″, E 102° 50′ 06.21″, 01.02.2009, 2♂ larvae. – LAO 1.2, Laos, Nam Mo, N 18° 51′ 17.90″, E 102° 50′ 32.40″, 01.02.2009, 1♂ larva, 2♀ larvae. – all N. Sangpradub leg.

Etymology

The species is dedicated to my dear friend and colleague Karen Bühler.

Male subimago

Three specimens are last instar male larvae. The following subimaginal features are therefore visible:

Base of antennal flagellum dilated, dilated part 0.4 times as wide and about as long as pedicel. Prosternal ridges forming a relatively short trapezoid. Segments 2 and 3 of foretarsus each with a moderate apico-median projection, segment 4 with two projections, a lateral and a median one. Abdominal segments with short triangular posterolateral processes. Sternite IX and subimaginal genitalia as in Fig. 9a. Penis broadly rounded. Forcipes short and broad, with a short tuft of thin spines (Fig. 9b).

Larva

Measurements and colouration

Male last instar larva: body length 2.7–3.5 mm, Sub-mature female larva, body length 5.0 mm.

Colouration of cuticle light yellowish brown to yellowish white. Only traces of pigments on head and pronotum.

Morphology

Cuticle: head and pronotum moderately granulated. Operculate gill densely provided with small denticles, partly net-meshed. Mesonotum with transitional structure.

Head: Genae not bulged. Pedicel with 1–3 small, pointed bristles. Mandibles with a broad dorsolateral field of very long, thin and bowed bristles. Two strong and pointed bristles in front of the eyes. Ratios of maxillary and labial palps and their parts see Table 1.

Thorax: Sides of pronotum straight, slightly diverging anteriorly, denticulated, with 2–3 long and thin bristles. Sides of mesonotum without an anterior-lateral nose-shaped projection. Bristles anteriorly of coxae sparse and very thin. Coxal processes semi-elliptical (Fig. 9g). Forefemur on dorsal side with a transverse row of elongated moderately spatulate bristles (4–5 anterior + 2–3 posterior) (Fig. 9f); somewhat longer bristles on hind margin apically from the transverse row. Mid and hind femora with thin, moderate or long marginal bristles. Dorsal side with 3–4 short spatulate bristles, some mid femora basally with few short thin bristles. Foretarsus ventrally with 4–6 small simple bristles. Mid tarsus with a row of about 6–7 simple bristles, the apical one pinnate, hind tarsus with an inner row of 6–8 simple bristles and an outer row of 3–5 pinnate bristles. All claws slender and slightly bowed, basally 0–2 very small denticles, hind claw with a dense row of microdenticles or pins, basal often with one or two small denticles (Fig. 9e).

Abdomen: Abdominal segments with posterolateral processes of moderate length, on segments VIII and IX shorter. Segment VII with 7–8 long bristles. Segment VIII with 4–5 shorter and segment IX with 2–4 short bristles (Fig. 9a). Tergum II with a broadly rounded, flat posteriomedian process. Hind margin of tergum VII with about 20 thin bristles, most of them long. Tergum VIII with about 15 moderate to long bristles, few short and blunt. Hind margin of tergum IX and X with small denticles. Hind margin of sternum IX broadly rounded, with moderate bristles, the apical ones bent medially, some of them bifurcated. Shagreen on dorsal side composed of few denticles immediately on hind margin (hardly visible) (Fig. 9a). Operculate gill (Figs 9c, 11 right) with moderate and short bristles on lateral margin. Hind margin with long and very long bristles, moderate ones between them. On postero-lateral corner 8–10 short and blunt bristles can be found between moderate ones. Y-shaped ridges weakly developed, median ridge posteriorly reduced, with 6–7 moderate, blunt and parallel-sided bristles in their basal third (Figs 9c, d). Ventral row of microtrichia almost reaching the postero-medial corner of the gill (Figs 9c, 11, left). Microtrichia oval with very fine filaments (Fig 11, right). Gill I a little more than half as long as gill II.

Differential diagnosis

Caenis karenae can be distinguished from all other Caenis species by the following combination of characters: Male: Base of antennal flagellum dilated. Segments 2 and 3 of foretarsus each with an apico-median projection. Penis lobes broadly rounded (Fig. 9a). Forcipes short and very broad, with a short tuft of thin spines (Fig. 9b).

Larva: Claws slender, slightly bowed, basally with 0–2 very small denticles, hind claw additionally with a long, dense row of microdenticles or pins (Fig. 9e). Median ridge on operculate gill in its basal fourth with about 6 moderate spatulate bristles directed postero-laterally (Fig. 9c). Shagreen on dorsal side of sternum IX with few denticles immediately on hind margin (hardly visible) (Fig. 9a).

Kimmins (1947: 99)

Malzacher (2015: 383)

Material examined

CHI 1.1, Thailand, Yasothon Prov., Tha Sai Mae Su Jin, Chi River, 15° 48′ 23.90″N, 104° 07′ 09.80″E, 24.06.2003, 1♂larva. – POG 1.7, Thailand, Khon Kaen Prov., Ban None Karm Phae, Phong River, 16°43′ 52.43″N, 102°46′16.55″E, 10.02.1996, 1♂ larva. – POG 1.8, Thailand, Maha Sarakham Prov., Ban Kui Pang, Phong River, 16° 23′ 31.70″N, 102°57′19.20″E, 1 ♂larva, 1♀ larva. – POG 2.10, Thailand, Khon Kaen Prov., Ban Kut Kwang, Phong River, 16° 42′ 16.70″N, 102° 49′ 29.40″E, 24.02.2011, 1♀ larva. – POG 3.3, Thailand, Khon Kaen Prov., Ban Or Noi, Phong River, 16° 44′ 01.41″N, 102° 49′ 09.07″E, 13.07.2013, 1♂ larva, 1♀ larva. – MRC 1.3, 1.4, 1.5, Thailand, Nakorn Phanom Prov., Nam Kham River, 17.06.2013, 4 larvae ♀. – MRC 2.2, Thailand, Ubon Ratchathani Prov., Kong Chiam District, Mun River, 04.04.2015, 1♀ larva. – POG 1.11, Thailand, Khon Kaen Prov., Ban Kut Kwang, Phong River, 16° 42′ 16.70″N, 102° 49′ 29.40″E, 24.02.2011, 1♀ larva. – all N. Sangpradub leg.

Male subimago

Two specimens are male last instar larvae. The following subimaginal features are therefore visible and can be compared with males (see description in Malzacher 2015: pp. 38):

Base of antennal flagellum not dilated. Prosternal ridges forming a cone-shaped figure, sides slightly convex. Segments of foretarsus apically not broadened, without small spines. Abdominal segments with short posterolateral processes. Sternite IX and subimaginal genitalia as in Fig. 10a. Penis with rounded lobes and a broadly v-shaped ventral sclerite. Styliger sclerite brownish, medially pale, with two apophyses of moderate length. Forcipes straight, apically with few short thin spines.

Larva

Measurements and colouration

Male larva of last instar, body length 2.8–3 mm. Female larva of last instar, body length 5.0 mm.

Colouration of cuticle: A relatively pale species, from whitish beige to light yellowish brown.

Epidermal pigmentation: There are few small brown pigment spots: two paramedian pairs on pronotum and mesonotum, two spots near inner margin and base of wing buds, three in a line parallel to postero-lateral margin of operculate gill and three in a transverse row on abdominal terga IX and X. Pigment spots also on paraterga. In strongly coloured specimens they are enlarged to longitudinal dashes. Those specimens also show pigments on hind margin of head and pairs of marks on abdominal sterna.

Morphology

Cuticle: Scattered with granules, on operculate gills and abdominal terga more or less denticulated. Surface scattered with long thin bristles.

Head: Genae scarcely bulged. Pedicel with few very thin and short bristles. Mandibles dorsolateral with thin, moderate and bowed bristles. No bristles in front of the eyes. Ratios of maxillary and labial palps and their parts see Table 1.

Thorax: Sides of pronotum straight, converging anteriorly, sometimes slightly concave or with a flat indentation near forecorner; nearly smooth, one or two thin bristles. Sides of mesonotum without an antero-lateral nose-shaped projection. No bristles anteriorly from coxae. Coxal processes inconspicuous, sickle-shaped. Forefemur on dorsal side with a longitudinal row of thin or long bristles, no transverse row. All femora with thin, moderate or long bristles on hind margin and shorter ones on foremargin. Dorsal side of mid and hind femora with few long thin bristles, sometimes lacking. Tibiae marginally with moderate bristles, some longer ones on dorsal side. Foretibia additionally with a dorsomedial row of long thin bristles. Fore- and mid tarsus ventrally with 8–10 more or less pinnate bristles, clearly longer than in other species. Hind tarsus with an inner row of 6 short simple bristles and an outer row of 8 long pinnate bristle. Foreclaw slender and slightly bowed, with about 10 strong denticles (Fig. 10d). Mid and hind claw broader, apically strongly bowed with 12–15 strong denticles (Fig. 10e).

Abdomen: Posterolateral processes on abdominal segments VII–IX short to moderate, the anterior ones abruptly longer (VI 3 times as long as VII); segments V-VII with 8–10 long, thin bristles, segment VIII with 1(-2), segment IX without (Fig. 10g). Terga I and II each with a cone-shaped posteriomedian process, on tergum I a little shorter (Fig. 10c). Hind margin of tergum VII with about 20 thin bristles, most of them long. Hind margin of terga VIII, IX and X with small denticles. Sternum IX triangularly protruding posteriorly, with moderate bristles laterally, the apical ones shorter and bent medially, some of them bifurcated. Shagreen not visible (Fig. 10a). Operculate gill (Fig. 6b) marginal with about 100 moderate and long thin bristles (in other species the number is 55–85, in Fig. 6b only one in four bristles are figured), the longest on lateral and hind margin. Few shorter bristles on postero-lateral corner. Y-shaped ridges weakly developed. Median ridge a little stronger, with 6–8 very long pointed bristles in its basal two third. Median hind corner of operculate gill more or less protruding posteriorly. Ventral row of microtrichia ends near posteromedial corner of the gill (Fig. 10b). Microtrichia elongated, parallel-sided, or more or less rounded, with filaments all over the outline (Fig. 12). Gill I 0.7 times as long as gill II.

Egg

Broadly oval (Fig. 13a). Chorion with fine pores and scarcely visible irregular net-meshes. Two epithemata; initial stage flat, forming a coil of fine threads, ending in very tiny knobs, surrounded by the coil (Figs 13a, above, 14). Later on, epithemata become more or less uncoiled (Fig. 13a, below). Micropyle long and thin, without visible sperm-guide (Fig. 13b).

Remarks: The species seems to be related to the West Palearctic Caenis lactea (see Malzacher 2015), supported also by larval features e. g. anteriorly converging sides of pronotum and hind margin of sternite IX triangular, posteriorly elongated (Fig. 10g). Both larvae can be distinguished by shape and setation of abdominal segments (compare Figs 10f and g).

Material examined

Holotype. ♂ (on microslide): SMNS_EPH_007789_M, PCB 2.3, Thailand, Petchabun Prov., Huai Hin Lad, Nam Nao National Park, 11.02.1998.

Etymology

The species epithet refers to the blunt apex of forcipes, from Latin obtusus, blunt.

Male imago

Measurements, ratios and colouration

Body length: 2.2 mm; wing length: 2.0 mm; length of foreleg: 2.0–2.3 mm. Ratio of forefemur: foretibia = 0.56–0.58; ratio of foretibia: foretarsus = 1.20–1.27; ratio of foreleg: hind leg = 1.98–2.00; ratio of first segment of foretarsus: 2nd: 3rd: 4th: 5th = 1: 3.9–4.3: 1.9–2.0: 1.1–1.2: 0.8–1.0.

Colouration of cuticle: Thorax brownish-yellow, scutellum and sutures yellowish-brown; other parts yellow to white. Epidermal pigmentation: Vertex with two more or less intense grey transverse bands. Abdominal terga laterally shaded with brown, terga III–VI with narrow transverse brown bands. Other parts without pigments. (Fig. 15).

Morphology

Head (Fig. 16d): Foremargin between lateral and frontal ocelli convex. Eyes and lateral ocelli relatively small. Eyes spherical. Frons strongly bent ventrally, frontal ocellus nearly invisible in dorsal view. Pedicel elongated, length about 2.7x width. Base of antennal flagellum not dilated (Fig. 16c).

Thorax: Prosternal ridges narrow, forming an anteriorly open trapezoid with concave sides (Fig. 16e). Segments 2–3 of foretarsus each with an apico-median tongue-shaped projection, segment 4 additionally with a short lateral projection: projections with few very small and thin spines or without (Fig. 16f).

Abdomen: Tergum II without finger-like process. Lateral filaments short or very short.

Genitalia and sternum IX as in Fig. 16a. Penis lobes short, broadly rounded. Styliger sclerite broad with short apophyses. Forcipes relatively short, slender, apically rounded and more or less bent medially; surface scattered with small short bristles (Fig. 16b). Distance between the most lateral points of the forceps bases about 2.5 times of forceps length. Sides of sternum IX strongly convex. Postero-lateral processes very short. Basolateral sclerites posteriorly with a small bump.

Differential Diagnosis

Caenis obtusostilata can be distinguished from all other species of Caenis by the following combination of characters: Forcipes apically rounded, without spines (Fig. 16b). Penis lobes short and rounded (Fig. 16a). Base of antennal flagellum not dilated (Fig. 16c). Tarsomeres 2–3 of foretarsus each with an apico-median tongue-shaped projection, segment 4 with two projections, a lateral and a median one; projections with few very small and thin spines or without (Fig. 16f). Frons strongly bent ventrally, frontal ocellus nearly invisible in dorsal view (Fig. 16d).

Material examined

Holotype. ♂ (on microslide): SMNS_EPH_007788_M SKK 2.1, Thailand, Sakon Nakhon Prov., Keng Mod Dang, Phu Phan National Park, 12.02.1998.

Paratype: same data as Holotype, 1♂ SI.

Etymology

The species epithet refers to the acute apex of forcipes, from Latin acutus, pointed, acute.

Male subimago

Measurements, ratios and colouration

Body length: 2.5–2.7 mm; wing length: 2.3–2.5 mm; forelegs lacking: Cerci about 2 times as long as body, terminal filum about 3 times.

Colouration of cuticle: Thorax brownish-yellow, other parts yellow to white.

Epidermal pigmentation: no pigments can be observed.

Morphology

Head (Fig. 16k): Foremargin between lateral and frontal ocelli convex. Outline of eyes elliptical. Base of antennal flagellum dilated, dilated part 0.4 times as wide and a little longer as pedicel (Fig. 16j).

Thorax: Prosternal ridges narrow, forming a broad trapezoid with slightly concave sides; anteriorly with a transverse strip (Fig. 16l). Segments 2–4 of foretarsus each with an apico-median tongue-shaped projection, segment 4 without a short lateral projection (visible in foreleg of subimago).

Abdomen: Tergum II without finger-like process. Lateral filaments short or very short.

Genitalia and sternum IX as in Fig. 16g. Penis lobes short, broadly rounded; penis heart-shaped. Styliger sclerite broad with very short apophyses, foremargin slightly convex. Forcipes straight, of moderate length, basal part more or less parallel sided, evenly narrowed towards the tip that consists of 1–2 (3) short spines (Figs 16h, i); the whole surface densely provided with small short bristles. Distance between the most lateral points of the forceps bases about 1.7 times the forceps length. Sides of sternum IX straight, slightly convex. Postero-lateral processes short and broadly rounded. Lateral and basolateral sclerites anteriorly strongly converging. (Fig. 16g).

Differential Diagnosis

Caenis acutostilata can be distinguished from all other species of Caenis by the following combination of characters: Forcipes straight, basally parallel-sided, apically converging, with 1–3 short spines (Fig. 16h, i). Penis heart-shaped (Fig. 16g). Base of antennal flagellum dilated (Fig. 16j). Segments 2–3 of foretarsus each with an apico-median tongue-shaped projection, segment 4 with two projections (as in Fig. 16f). Lateral and basolateral sclerites anteriorly strongly converging (Fig. 16g). Pale species, genitalia uncoloured.

Type species: Elatosara phanomensis Malzacher, n. sp.

Differential Diagnosis

Elatosara can be characterised and distinguished from all other genera of Caenidae by the following combination of characters:

Males: Prosternal ridges divided in several thin ones, forming a bell-shaped figure (Fig. 17c). – Forceps of moderate length, apically converging and rounded, without longitudinal folds or ridges (Fig. 17b). – No functional unit of forceps and lateral sclerite.

Larva: Thorax not broadened. – Head without ocellar tubercles and microscopic pits. – Outline of head slightly bulged in lateral view (Fig. 17f). – Clypeus scarcely protruding anteriorly, without setation (Fig. 17f). – Maxillar and labial palps three-segmented, short. – Segments 2 and 3 of labial palp subequal in length. – Legs not narrow and slender. – Fore tibia and fore tarsus without filtering setae. – Mid and hind tibia ventrally without long bristles. – Femora marginal with long or very long thin bristles (Fig. 17e); similar bristles forming transverse row on fore femur (Fig. 17d) – Operculate gill ventrally with an irregular band of simple scale-shaped microtrichia, clusters of spines and single spines (Figs 18, 19). – Band does not reach hind margin of gill (Fig. 18). – Number of more-branched filaments on gill III(-V) reduced, only 7–9 filaments with 3 or more branches. – Lateral spines of abdomen not bent dorsally. – Posterior part of sternum IX rounded, not shortened (Fig. 17a). – Abdominal terga VII–IX without mediolongitudinal ridge. – Hind margin of sternum IX without a bi-pointed process with concave margin between the points.

Etymology

Elatos, a figure of the Greek mythology, was the father of Caenis. The ending “-ara” is common in the tribe Clypeocaenini, to which the genus has to be added.

Material examined

Holotype. ♂ larva (on microslide): MRC 2.3, Thailand, Nakhon Phanom Prov., Mekong River, 01.04.2015, SMNS_ EPH_007793_M.

Paratypes. MRC 2.3, Thailand, Nakhon Phanom Prov., Mekong River, 01.04.2015, 1♀ larva. MRC 1.5, Thailand, Nakhon Phanom Prov., Nam Kham River, 17.06.2013, 1♂larva. – all N. Sangpradub leg.

Etymology

The species name refers to the Thai word phanom that means hill, because of the hilly region where the specimens are found.

Male subimago

Two specimens are male last instar larvae. The following subimaginal features are therefore visible:

Base of antennal flagellum not dilated. Prosternal ridges divided into several thin ones, forming a bell-shaped figure. (Fig. 17c). Segments of foretarsus apically not broadened, without small spines. Abdominal segments with very short posterolateral processes. Subimaginal genitalia as in Fig. 17a. Penis narrow, with broadly rounded lobes, apico-ventral part heart-shaped. Styliger sclerite with two inconspicuous short apophyses. Forcipes of moderate length, apically converging and rounded (Fig. 17b).

Larva

Measurements and colouration

Male larva of last instar, body length 2.5–2.8 mm, cerci length 1.5 mm.

Colouration of cuticle: Head, pro- and mesonotum and operculate gill brownish yellow. Other parts whitish.

Epidermal pigmentation: not visible.

Morphology

Cuticle: Head, pro- and mesonotum slightly granulated. Abdominal terga denticulated. Surface scattered with long thin bristles. Operculate gill with denticles joint by net meshes.

Head: Outline of head slightly bulged in lateral view (Fig. 17f). Genae slightly bulged. Pedicel with 3–4 moderate bristles. Mandibles dorsolateral with relatively short, thin and bowed bristles. No conspicuous bristles in front of the eyes. Maxillary palp short, length to width ratio of segment 3: 3.5–4.0 (5.0–6.0 in most other Caenis species). Labial palp segments 2 and 3 subequal in length.

Thorax: Sides of pronotum diverging anteriorly, slightly concave, denticulated, with few thin bristles. Sides of mesonotum without an antero-lateral nose-shaped projection. Coxal processes inconspicuous, sickle-shaped. Forefemur on dorsal side with an oblique transverse row of long or moderate thin bristles (Fig. 17d). Mid and hind femora with long or very long thin bristles on hind margin and somewhat shorter ones on foremargin; dorsal side with few long thin bristles (Fig. 17e). Tarsi ventrally with 5–7 moderate, strong and simple bristles. Foreclaw slender and slightly bowed. Mid and hind claw basally broader, apically more or less bowed. All claws with 5–7 small or very small denticles, often nearly invisible.

Abdomen: Posterolateral processes on abdominal segments short and triangular, V and VI a little longer. Segments V–VII with 6–7 long bristles, segment VIII with about 5 bristles of moderate length, segment IX with about 3 shorter ones. Sides of segment IX nearly parallel, straight or slightly convex (Fig. 17a). Tergum II with a cone-shaped, erect, posteromedian process. Hind margin of tergum VII with about 12, of tergum VIII with about 8 thin long bristles. Hind margin of terga IX and X with small denticles. Hind part of sternum IX obtuse angled triangular, with broadly rounded tip, marginally with long to moderate bristles, the apical ones shorter and bent medially, at the top a couple of short bifurcated bristles (Fig. 17a). Shagreen not visible. Operculate gill square-shaped, with very broadly rounded postero-lateral corner; this part with short, often spatulate bristles; lateral margin with moderate and long thin bristles, the longest towards the basal end; other long bristles on postero-median corner; inner margin with moderate bristles (Fig. 18). Y-shaped ridges well developed, particularly the median one; base of the latter with about 4 strong pointed bristles of moderate length. Ventral side of operculate gill with an irregular band of simple, scale-shaped microtrichia, clusters of spines and single spines that do not reach hind margin of gill (Figs 18, 19). Gill I about three fourth the length of gill II. Gill III–V with about 8 filaments with 3 branches each.

Type species: Thainis kalimaenoides Malzacher, n. sp.

Differential Diagnosis

Thainis can be characterised and distinguished from all other genera of Caenidae by the following combination of characters:

Larva: Body slender and elongated, outline evenly curved (Fig. 20). – Head without ocellar tubercles and microscopic pits. – Besides a slight anterior protrusion of clypeus, forming a straight foremargin (Fig. 20, frame), outline of head not bulged in lateral view. – Clypeus without setation. – Maxillar and labial palps three-segmented (Figs 22, 30). – Maxillary palps elongated and narrowed with a conical segment I and more or less s-shaped, coiled segments II and III (Figs 22a, 30a). – Segment 3 of labial palp very short, with oblique dividing line to segment 2; 2 and 3 together oval (Fig. 22b, 30b) – Legs not narrow and slender. – Claws very narrow and slender (Figs 24, 32). – Only hind claws with basal denticles. – Operculate gill ventrally with a regular row of well-developed scale-shaped microtrichia, reaching hind margin of gill; basal area with long pinnate bristles (Figs 25, 27; 33). – Gill III(–V) with very long filaments, most of them with 3 or 4 branches (Fig. 36), dorsal and ventral side densely provided with long thin bristles. – Lateral spines of abdomen not bent dorsally. – Posterior part of sternum IX not shortened, with an apical indentation (Figs 21a, e). – Abdominal terga VII–IX without mediolongitudinal ridge.

Etymology

The genus name is a combination of Thailand and Caenis.

Material examined

Holotype. ♀ larva (on microslide): CHI 3.1, Thailand, Maha Sarakham Prov., Ban Muang, Chi River, N 16° 14′03.72″, E 103° 25′ 15.32″, 17.06.2003, SMNS_EPH_007790_M.

Other material. CHI 1.2, Thailand, Yasothon, Tha Sai Mae Su Jin, Chi River, N 15° 48′ 23.90″, E 104° 07′ 09.80″, 28.02.2003, 1 ♀ larva. – all N. Sangpradub leg.

Etymology

The species name refers to similarities with the genus Kalimaenis.

Larva

Measurements and colouration

Female larva, subadult, body length 7.0 mm, cerci length 3.0 mm.

Colouration of cuticle: yellowish-brown. Epidermal pigmentation: specimens are badly preserved so that pigmentation is not visible.

Morphology

Cuticle: Head, pro- and mesonotum granulated, without chloride cells and fine bristles (compare next species). Abdominal terga denticulated, with few blunt or spatulate bristles. Tergum VII densely provided with moderate, nearly parallel sided blunt bristles. Operculate gill with sharp denticles, scattered with moderate blunt bristles.

Habitus: slender, elongated. Outline of body evenly curved (Fig. 20).

Head: Besides a slight anterior protrusion of clypeus, forming a straight foremargin (Fig. 20, frame), outline of head not bulged in lateral view. Genae long, slightly bulged. Pedicel covered with short thin bristles. Mandibles dorsolateral without conspicuous bristles. Two blunt bristles in front of the eyes. Segments 2 and 3 of maxillary palp very long, as long as forefemur; segment 1 apically slightly converging; segment 2 and 3 coiled (Fig. 22a). Labial palp segments 2 and 3 together oval, with oblique dividing line; about 3 times as long as wide (Fig. 22b).

Thorax: Sides of pronotum more or less converging anteriorly (Fig. 20), nearly smooth. Foreleg a little shorter than hind leg (Foreleg / hind leg = 0.8). Coxal processes semicircular, margins denticulated with few thin bristles (Figs 21c, d). Forefemur on dorsal side with irregular transverse band of moderate, flat, blunt, and parallel-sided bristles; hind margin basally from transverse row with numerous very long hair-like bristles, as long as femur width; dorsal side basally from transverse band scattered with moderate and long, very thin bristles (Fig. 21b). Hind margin of mid and hind femora densely provided with long to moderate bristles, the longest hair-like, the shorter ones blunt. Those blunt bristles also on foremargin (Fig. 23) and on anterior part of dorsal side. Foretibia on foremargin with a row of long to moderate pointed bristles apically ending in a group of shorter, more or less pinnate ones. Few similar bristles neighboured on tarsus base. Tibia on antero-dorsal side with about 10 long and thin bristles, the longest nearly half as long as tibia. Hind tibia marginally with long and moderate bristles. Foretarsus ventrally with a row of about 10 moderate pinnate bristles, the basal ones only slightly pinnate. Mid tarsus with a row of about 13 simple bristles, hind tarsus with an irregular row or band of 14–17 slightly pinnate bristles. All claws very long, slender and slightly bowed. Foreclaw without denticles (as Fig. 24b). Mid claw basally with about three very small denticles. Hind claw basally with 5–8 small denticles (Fig. 24a).

Abdomen: Posterolateral processes on abdominal segments short (Fig. 20). Segments V-VII on lateral margin densely provided with moderate to long blunt bristles, between them a couple of short strong and blunt ones. Segments VIII and IX with shorter bristles, on IX often very short (Fig. 21a). Tergum II with a flat, triangular, dorsally lifted posteromedian process. Tergum VII dorsally with short to moderate blunt bristles, tergum VIII with fewer short, blunt ones. Hind margin of tergum VI densely provided with about 60 moderate, pointed bristles, of tergum VII with short to moderate blunt bristles, of tergum VIII with few very short blunt to spatulate bristles, and small rounded denticles. Hind margin of terga IX and X with denticles more or less pointed. Hind part of sternum IX triangular, broadly rounded, apically with a small semicircular indentation, marginally with moderate, thin bristles, the apical ones shorter, a few of them bifurcated (Fig. 21a). A large dorsal shagreen field consists of densely arranged, very sharp denticles (dotted line in Fig. 21a). Operculate gill nearly as long as wide (Fig. 25), marginally with long, pointed, thin bristles, the longest ones on posteromedial corner and on basal part of lateral margin. The latter also with moderate, blunt, often apically broadened bristles, on posterior part all of them broadened (Fig. 28). Bristles on hind margin densely provided with fine filaments (Fig. 29). Basal part of median ridges well developed with about 6 moderate, strong bristles, other parts of Y reduced. Ventral side of operculate gill with a regular row of elongated scale-shaped microtrichia (Fig. 26), relatively close to lateral margin, which nearly reaches posteromedial corner (distance to margin length of one microtrichium) (Fig. 25); basal area with long, pinnate bristles (Fig. 27a). Gill I very short, only about 0.2 times as long as gill II, without bristles. Gill III(–V) with very long filaments, the longest nearly twice as long as gill corpus; widely projecting hind margin of operculate gill; most filaments with 3 or 4 branches; gill corpus dorsally and ventrally densely provided with very long and thin bristles.

Material examined

Holotype.♀larva(onmicroslide):SMNS_EPH_007791_M, MUN 1.2, Thailand, Nakorn Ratchasima Prov., Ban Muang, Mun River, N 15° 13′ 40.00″, E 102° 28′ 53.80″, 10.12.2003.

Paratypes. MUN 1.1, MUN 1.2, same data as Holotype, 3 larvae.

Other material: POG 1.2, Thailand, Khon Kaen Prov., Ban Nong Chik, Phong River, 03.02.1996, 2♀ larvae. – POG 1.4, Thailand, Loei Prov., Ban Na Noi, Phong River, 16°48′ 59.41″N, 101°48′ 23.91″E, 21.08.1996, 1♀ larva. – all N. Sangpradub leg.

Etymology

The species name refers to Mun River, where the holotype has been found.

Larva

Measurements and colouration

Female larva, submature, body length 8.0 mm, cerci length 4.5 mm.

Colouration: specimens are badly preserved so that colouration cannot be described.

Morphology

Only characters that differ from the species above are described.

Cuticle: Head, pro- and mesonotum more or less granulated with numerous chloride cells and fine bristles. Abdominal terga slightly denticulated, with numerous very thin bristles of different length. Tergum VII densely provided with long thin bristles apically more or less pinnate. Operculate gill more or less denticulated, scattered with very thin bristles.

Head: Genae short, slightly bulged. Segments 2 and 3 of maxillary palp shorter, 0.7–0.8 times as long as forefemur; segment 2 and 3 scarcely coiled or not (Fig. 28a). Labial palp segments 2 and 3 together broadly oval, about 2.6 times as long as wide (Fig. 30b).

Thorax: Ratio Foreleg / hind leg length = 0.75. Bristles of transverse row on dorsal side of forefemur long and pointed. Foretibia apicomedially with a tuft of about 15 strong, pointed and pinnate bristles more or less bent medially, few similar bristles neighboured basally on first tarsal segment (Fig. 31). Dorsal side of tibia without long and thin bristles. Hind tibia without long and moderate bristles on hind margin. All tarsi ventrally with a band of numerous pinnate bristles. Number of bristles: foretarsus 14–20 (24), mid tarsus 17–22 (26), hind tarsus 20–30 (37). Mid claw with about 7 small, basal denticles. Hind claw basally with numerous very small denticles, most of them serrated with two or three tips (Fig. 32).

Abdomen: Longer bristles on lateral margin of abdominal segments pointed, between them 6–10 short strong and blunt bristles. Tergum VII dorsally with moderate to long thin, apically slightly broadened bristles, tergum VIII with long, hair-like bristles. Hind margin of tergum VI without bristles, of tergum VII and VIII with moderate bristles, basally relatively broad and apically very thin. Hind margin of terga IX and X with denticles. Hind margin of sternum IX apically with a broad, v-shaped indentation (Fig. 21e). A relatively narrow shagreen field composed of densely arranged sharp denticles (dotted line in Fig. 21e). Operculate gill clearly longer than wide (Fig. 33). Row of microtrichia on ventral side of operculate gill runs close to lateral and hind margin; often microtrichia extend gill margin (Fig. 34a, b). Pinnate bristles from basal area with two long strong apical spines (Fig. 27b). Gill I one third the length of gill II, with 8–10 long thin bristles. Gill III(–V) with long filaments, the longest 1.5–1.7 times as long as gill corpus (Fig. 35).

Malzacher (2013: 32)

Type species: Kalimaenis sibylliana Malzacher, 2013

The genus can be characterised and distinguished from all other genera of Caenidae by the following combination of characters:

Larva. Surface (dorsal and ventral side) strongly granulated. – Head without ocellar tubercles and microscopic pits but with ridges or bulges. –Clypeus anteriorly protruding, without setation (Fig. 36). – Maxillar and labial palps three-segmented. – Maxillary palp very slender, segment I apically converging, segments II and III coiled (Fig. 37). – Segment III of labial palp very short, with oblique border to segment II (Fig. 37). –Legs narrow and slender. – Foreleg clearly shorter than hind leg. – Foretibia and foretarsus without very long bristles. – Hind claws with groups of micro-denticles fused together (in the here described species less visible, Fig. 39). – Gill I very short. – Operculate gill ventrally with a regular row of microtrichia, row ends well apart from hind margin of gill (Fig. 40). – Number of filaments on gills III–VI reduced; only about 7 filaments with 3 or more branches on gill III. – Lateral spines of abdomen not bent dorsally. – Abdominal terga VII–IX without mediolongitudinal ridge. – Hind margin of sternum IX without a bi-pointed process with concave margin between the points.

Material examined

Holotype. ♀ larva (on microslide): SMNS_ EPH_007792_M, KKJ 1.6, Thailand, Kanchanaburi Prov., Pa La Au6, Kaeng Krachan National Park, 03.04.2008, KKJ 1.5, Thailand, Kanchanaburi Prov., Pa La Au5, Kaeng Krachan National Park, 10.02.2009, 1♀ larva. – all N. Sangpradub leg.

Etymology

The species epithet refers to the slender body-shape, from Latin procerus, slender.

Larva

Measurements and colouration

No last instar or submature larva available.

Colouration of cuticle: yellowish-brown Epidermal pigmentation: apart from eyes and ocelli no pigments visible.

Morphology

Body: slender and narrow (Fig. 36).

Surface: dorsal and ventral side strongly granulated, head and thorax mainly with round knobs and square or pentagonal elevations, abdomen with scaly triangular denticles, also on femora, and modified, very short, club-shaped bristles (Fig. 38). Because of these triangular denticles, body outlines appear strongly granulated or denticulated.

Head (Fig. 37, ventral side): Genae broadly bulging out. Mouthparts shifted posteriorly. Clypeus slightly protruding anteriorly, protrusion with straight foremargin (Fig. 21h, 36). Labrum broadly elliptically rounded. Mandibles without setation. Maxillary palp very slender, segment I apically converging, segments II and III coiled. Segment III of labial palp very short, with oblique border to segment II; segment I short and rounded (Fig. 37).

Thorax: Pronotum broadly rectangular, lateral sides parallel, straight, forecorners protruding anteriorly; fore- and hind margin in dorsal view straight and parallel (Fig. 36); foremargin of prosternum medially strongly emarginate. Legs narrow and slender. Forelegs clearly shorter than hind legs (Fig. 36). Coxal processes forming inconspicuous, denticulated ridges. Femora and tibiae with very short and tiny marginal bristles looking like small knobs. Transverse row on forefemur composed of only 3–5 very short spatulate bristles. Fore- and mid tarsus ventrally with inner row of about 9–11 bristles, the basal ones short and pointed, the apical long and pinnate. Hind tarsus additionally with an outer row of 4–6 unipinnate bristles, pinnae directed medially; both rows lie very close to each other. Claws slender and scarcely bowed; fore- and mid claws without denticulation; hind claws with very fine micro-denticles forming blurred groups (Fig. 39).

Abdomen: Abdominal segments with short posterolateral processes; on segment IX nearly totally reduced (Fig. 36). Lateral bristles very short and blunt, on segment VIII and IX knob-like, often nearly invisible. Posteriomedian process of tergum II short, triangular and pointed. Hind margin of tergum VII–X strongly denticulated. Hind margin of sternum IX domed, with a deep indentation of different width (Fig. 21g). Gill I very short, about 0.2x the length of gill cover. Operculate gill (Fig. 40) without bristles on lateral margin, but with few short and thin bristles on median margin. Hind margin densely provided with moderate, broad and flat bristles, increasing in length from posterolateral to posteromedial corner; lateral margins densely provided with fine filaments; filaments of neighbouring bristles overlapping (Fig. 42). Y-shaped ridges well developed, connected in the middle of the gill; medial ridge moderately keeled with about 8 blunt bristles at base of keel. Ventral row of microtrichia not reaching hind margin of gill (Fig. 40). Microtrichia inconspicuous, more or less semicircular, with broad bases (Fig. 41). Small single spines on basal half of ventral surface. Number of filaments on gills III–VI reduced; gill III with about 26 filaments, only 6–7 with 3 or more branches.