Cloeon bengalense Kimmins, 1947

Noenrimnong, Chayanon, Suttinun, Chanaporn, Tungpairojwong, Nisarat & Boonsoong, Boonsatien, 2026, Taxonomic insights into the diversity of Cloeon Leach, 1815 (Ephemeroptera, Baetidae) in Thailand, ZooKeys 1266, pp. 1-39 : 1-39

publication ID	https://doi.org/10.3897/zookeys.1266.176616
publication LSID	lsid:zoobank.org:pub:8478A1BF-2692-4B88-986C-3751CCC8E056
DOI	https://doi.org/10.5281/zenodo.18157565
persistent identifier	https://treatment.plazi.org/id/C6283AC3-18BA-500D-A292-34AB9C79A09D
treatment provided by	ZooKeys by Pensoft
scientific name	Cloeon bengalense Kimmins, 1947
status

Treatment

Cloeon bengalense Kimmins, 1947 View in CoL

Figs 1 A – C View Figure 1 , 6 A, B View Figure 6 , 8 A, B View Figure 8 , 10 A, B View Figure 10 , 13 A, B View Figure 13 , 15 A, B View Figure 15 , 18 A – D View Figure 18 , 19 A – F View Figure 19 , 20 A – F View Figure 20 , 27 C View Figure 27 , 28 E View Figure 28 , 29 D View Figure 29

Cloeon bengalense Kimmins View in CoL : 95, figs 3, 7, 11 (original description, male and female).

Cloeon bengalense View in CoL : Kimmins 1971: 310 (list). Hubbard and Peters 1978: 8 (list). Hubbard and Srivastava 1984: 3 (list). Marcus 2019: 85, figs 1–4 (record).

Material examined.

• 4 nymphs, 5 female subimagos, 3 female imagos, Bangkok Prov., Luang Suwannawajokkasikij 100 th Year Park , 13°50'54.5"N, 100°34'15.1"E, 1. VIII. 2024, C. Noenrimnong leg. ( ZMKU) GoogleMaps ; • 4 nymphs, 1 male subimago, Bangkok Prov., Varunawan Park , 13°50'51.1"N, 100°33'45.9"E, 25. X. 2024, B. Boonsoong & C. Noenrimnong leg. ( ZMKU) GoogleMaps ; • 8 nymphs, 1 female subimago, 2 male imagos, 3 female imagos, Bangkok Prov., Information Building 50 Years , 13°51'11.6"N, 100°34'11.9"E, 12. I. 2025, C. Noenrimnong leg. ( ZMKU) GoogleMaps ; • 7 male subimagos, 1 female subimago, Lop Buri Prov., Huai Som , 14°51'52.3"N, 100°51'28.1"E, 19. I. 2025, A. Wongyam leg. ( ZMKU) GoogleMaps ; • 7 nymphs, 1 female imago, Chachoengsao Prov., Sao Cha-Ngok , 13°41'43.1"N, 101°09'13.5"E, 8. XI. 2024, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 3 nymphs, Prachin Buri Prov., Kabin Buri , 13°59'04.3"N, 101°45'11.4"E, 15. V. 2025, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 4 nymphs, 1 male subimago, 2 male imagos, 1 female imago, Nakhon Ratchasima Prov., Chateau de Khaoyai , 14°30'48.6"N, 101°27'06.0"E, 29. XI. 2024, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 2 nymphs, Maha Sarakham Prov., Nong Bua Kaeo , 15°31'56.4"N, 103°18'26.0"E, 16. V. 2025, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 3 nymphs, Buri Ram Prov., Mafueang Phutthaisong , 15°29'54.0"N, 103°02'58.2"E, 16. V. 2025, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 14 nymphs, Khon Kaen Prov., Sithan Lake KKU , 16°26'41.1"N, 102°48'55.0"E, 1. IV. 2024, N. Tungpairojwong leg. ( KKU) GoogleMaps ; • 22 nymphs, Khon Kaen Prov., Fisheries Pond KKU , 16°27'31.5"N, 102°48'38.3"E, 1. IV. 2024, N. Tungpairojwong leg. ( KKU) GoogleMaps ; • 3 nymphs, 1 male subimago, 1 female imago, Khon Kaen Prov., Khot swamp , 16°26'06.1"N, 102°48'09.0"E, 17. V. 2025, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 5 nymphs, 1 female imago, Mukdahan Prov., Nut Pob Rim Kong Mukdahan , 16°31'53.7"N, 104°44'05.0"E, 18. V. 2025, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 1 female imago, Chiang Mai Prov., Faculty of Veterinary Medicine CMU , 18°45'32.2"N, 98°56'24.8"E, 21. X. 2025, C. Suttinun leg. ( ZMKU) GoogleMaps ; • 1 female imago, Kanchanaburi Prov., Kwai Noi River , 14°12'07.7"N, 99°03'36.4"E, 22. XII. 2024, B. Boonsoong & C. Noenrimnong leg. ( ZMKU) GoogleMaps ; • 6 nymphs, 1 male subimago, 1 female imago, Kanchanaburi Prov., The River Kwai Bridge Resort , 14°02'26.7"N, 99°30'26.6"E, 05. VII. 2025, B. Boonsoong leg. ( ZMKU) GoogleMaps ; • 3 male imagos, Ratchaburi Prov., Bua Resort Suanphueng , 13°31'30.0"N, 99°14'40.3"E, 15. III. 2025, C. Noenrimnong leg. ( ZMKU) GoogleMaps .

Descriptions

(in alcohol). Female imago (Fig. 6 A View Figure 6 ). See Kimmins (1947) for original description. The female imagos of this species can be distinguished by the pale green to yellowish-green head, which bears a pale green midline flanked by two dark brown longitudinal stripes covering most of the dorsal surface (Fig. 18 A View Figure 18 ). The thorax is similarly coloured, with a pale green to yellowish-green ground colour and a pale midline flanked by two continuous dark brown longitudinal stripes extending from the head to the abdomen (Fig. 18 A View Figure 18 ). The abdominal terga are green to yellowish-green, with dark brown to dark reddish-brown pigmentation. Terga II – IX have a pale midline flanked by a pair of pale spots or drop-shaped stripes; the lateral margins of anterior terga exhibit dark reddish-brown spots or short stripes, with those on segments III and VI extending almost to the lateral margins (Fig. 13 A View Figure 13 ). The abdominal sterna exhibit dark reddish-brown spots along the lateral margins of segments II – VIII (Fig. 15 A View Figure 15 ). The wings are hyaline, with dark brown venation in the costal and subcostal areas (Fig. 10 A View Figure 10 ).

Male imago (Fig. 6 B View Figure 6 ). See Kimmins (1947) for original description.

The male imagos are recognised by their orange-yellow compound eyes with olive-green lower portions (Fig. 8 B View Figure 8 ). The abdominal terga are translucent white, with segments III and VI bearing dark reddish-purple stripes extending nearly to the lateral margins; smaller paired stripes occur on segments II and V. Segments VIII – X are variably coloured from orange to dark brown (Fig. 13 B View Figure 13 ). The abdominal sterna of segments VIII and IX are white, while sternum X ranges from orange to dark brown (Figs 15 B View Figure 15 , 18 B View Figure 18 ). The wings are hyaline (Fig. 10 B View Figure 10 ).

Mature nymph (in alcohol): Body length 5.66–5.67 mm, terminal filaments 3.44–3.49 mm.

Head: Two rows of irregular brown spots (Fig. 1 A View Figure 1 ). Antennae mostly brown, with darker colouration at the base (Fig. 19 A View Figure 19 ).

Mouthparts: i). Mandibles: Molar area contains densely distributed molar teeth. Lateral margins have sparsely distributed hair-like setae. Large prostheca, inner incisors, and outer incisors (Fig. 19 B, C View Figure 19 ). ii). Labrum: Dorsal surface and half margins covered with hair-like setae. More than half of the surface contains sparsely distributed hair-like setae, with tufts of setae on either side of the anterior notch (Fig. 19 D View Figure 19 ). iii). Maxillary Palp: Segments I and II with sparsely distributed hair-like setae on the surface, while segment III with more widely distributed hair-like setae (Fig. 19 E View Figure 19 ). iv). Labial Palpi: Segment I longer than segments II and III. Segments I and II with sparsely distributed hair-like setae, while segment III with hair-like setae densely distributed around the terminal margin and longer and denser than those on other segments. Glossae and para-glossae with longer setae on the margins (Fig. 19 F View Figure 19 ).

Thorax: Irregular brown markings (Fig. 1 A View Figure 1 ).

Legs: Femora of all legs pale but with brown stripes near the apex and base, short setae on the surface and both margins. Tibiae and tarsi with brown bands near their bases, with short, sparsely distributed setae on the surface and dense, medium-sized setae along the inner margins (Fig. 20 A – C View Figure 20 ). Base of the claws (foreleg) expanded, with the basal half containing two rows of spines with gradation size (Fig. 20 D View Figure 20 ).

Abdominal terga: Green to yellowish-green, uniform dark brown to dark reddish-brown. Segments II to IX, anterior part with a pale midline flanked by a pair of pale spots or drop-shaped stripes. Segments II and V may appear darker, while segments IV and VII may appear slightly paler but still retain the patterns. More than half of the lateral margin of segment VIII has 6–8 spines; whole of the lateral margin of segment IX has 6–11 spines (Figs 1 A, B View Figure 1 , 20 E View Figure 20 ).

Abdominal sterna: Green to yellowish-green, segments VII to IX with red to pale red spots near the middle posterior part, while segment X appears darker (Fig. 1 C View Figure 1 ).

Caudal Filaments: Each segment has a ring of spines at joints. Cerci with long setae along the inner margins and large, long spines on the outer margins. Terminal filament shorter than cerci, and long setae along both margins (Figs 1 A View Figure 1 , 20 F View Figure 20 ).

Egg. Width 43.37 μm; height 68.12 μm; filament thickness ranging from 0.154 to 0.173 μm. Oval-shaped; surface uniformly covered with dense, long filamentous structures (Figs 18 C, D View Figure 18 ).

Distribution.

Northern Thailand ( Chiang Mai province); northeastern Thailand ( Buri Ram, Khon Kaen, Maha Sarakham, Mukdahan, and Nakhon Ratchasima provinces); central Thailand ( Bangkok and Lop Buri provinces); eastern Thailand ( Chachoengsao and Prachin Buri provinces); western Thailand ( Kanchanaburi and Ratchaburi provinces).

Remarks.

The adults of Cloeon bengalense were described by Kimmins (1947) based on materials from West Bengal ( India). This species has also been recorded in Singapore from the adult stage. Ours is the first record of this species in Thailand. In this study, we provide the first description of the egg structure and nymphal stage of C. bengalense . Additionally, we describe the smaller paired stripes that occur on segment V of the male imago, thereby supplementing the original description by Kimmins (1947).