A new species of Aegus Macleay, 1819 (Coleoptera: Lucanidae: Lucaninae: Aegini) from Thailand with checklist of the genus species from the country Author Pathomwattananurak, Wuttipon 1051 / 38 Wiang, Mueang Dist., Chiang Rai Province, 57000, Thailand Author Jiaranaisakul, Kawin Rabbit in the Moon Foundation, 399, Village No. 3, Suan Phueng, Ratchaburi, 70180, Thailand text Zootaxa 2024 2024-05-21 5453 3 341 358 http://dx.doi.org/10.11646/zootaxa.5360.3.8 journal article 10.11646/zootaxa.5453.3.2 1175-5326 11234118 285FAECF-D307-48F5-9FA1-DE6320EA0F7C Aegus chelifer Macleay, 1819 ( Figs. 1–5 , 18 , 22 , 29–30 , 34 , 39 , 45–50 ) Aegus chelifer Macleay, 1819: 113 . Type locality: Australasia? Van Roon 1910: 41 ; Arrow 1943: 141 ; Benesh 1960: 100 ; Bomans 1967: 321 ; Bomans 1970: 231 ; Bomans 1991: 144 ; Mizunuma & Nagai 1994: 281 ; Krajcik 2003: 12 ; Pinratana & Maes 2003: 235; Fujita 2010: 318 ; Huang & Chen 2017:249 . Aegus nitidus Boileau, 1899: 321 . Type locality: Borneo. Boileau 1913: 256 (as synonym). Aegus specularis Jakovlev, 1900: 633 . Type locality: Cochinchine: Saigon . Arrow 1943: 141 ; Benesh 1960: 100 (as synonym). Aegus specularis tonkinensis Kriesche, 1920: 101 . Type locality: Tonkin . Benesh 1960: 101 (as synonym). Aegus chelifer nitidus : Mizunuma & Nagai 1994: 281 (as subspecies); Krajcik 2001 , 55; Fujita 2010: 319 ; Huang & Chen 2017: 252. Aegus chelifer tonkinensis : Bomans, 1992: 186 (as variety); Huang & Chen 2017: 249 (as subspecies). Aegus chelifer crassodontus Bomans, 1992: 186 . Type locality: Annam . Huang & Chen 2017: 252 ; new synonym. Type material examined. Syntype of Aegus chelifer Macleay, 1819 ( ♂ , BMNH , Figs. 45–47 ), labeled: “Type // 1736 // Aegus chelifer Macleay australasia. 1736 // chelifer . // H. Bomans det., 1983 Aegus chelifer Macl. ♂ // BMNH(E) #610724 // NHMUK015534103”, examined through photographs provided by Keita Matsumoto . Holotype of Aegus chelifer crassodontus Bomans, 1992 ( ♂ , BMNH , Figs. 48–50 ), labeled: “ Holotype . // 25.5.1920 // Holotype // 6136 // Aegus ♂ macrodontus ANNAM , Lacro J.P. Lacroix det. 1977 // H. Bomans det., 1992 Aegus chelifer var. crassodontus n.sp. // H.E. Bomans BMNH(E) 1999-248 // NHMUK015534102”, examined through photographs provided by Keita Matsumoto . Additional material examined ( 12♂♂ , 5♀♀ ). Thailand : 1♂ ( WPC ), Chiang Rai Prov. , Boon Rawd farm, 15.IV.2022 , Wuttipon Pathomwattananurak leg. ; 3♂♂ , 1♀ ( WPC ), Chiang Rai Prov. , Wiang Pa Pao Dist. , local collector leg .; 1♂ ( WPC ), Nan Prov. , Bo Kluea Dist. , 2015, local collector leg .; 4♂♂ , 2♀♀ ( WPC ), Nakhon Ratchasima Prov. , Bua Yai Dist. , 28.XI.2023 , Uraiwan leg. ; 1♂ , 2♀♀ ( WPC ), Ubon Ratchathani Prov. , Khong Chiam Dist. , VII.2022 , Qiao-Zhi Yang leg. ; 1♂ ( WPC ), Chanthaburi Prov. , Tha Mai Dist. , Song Phi Nong , 4.XII.2020 , Suchatree Tangcharoenkitsakul leg. ; 3♂♂ , 1♀ ( WPC ), Chanthaburi Prov. , Pong Nam Ron Dist. , VIII.2022 , Qiao-Zhi Yang leg. ; 1♂ , 1♀ ( WPC ), Nakhon Si Thammarat Prov. , Nopphitam Dist. , 20.X.2023 , Chayaphol Phothaworn leg. Myanmar : 1♂ ( WPC ), Mon State , Ye , 11.X.2023 , Somkit Boonmak leg. Distribution. India , Bangladesh , China , Taiwan , Myanmar , Vietnam , Thailand , Laos , Cambodia , Malaysia , Singapore , and Indonesia ( Mizunuma & Nagai 1994 ; Pinratana & Maes 2003 ; Fujita 2010 ; Huang & Chen 2017 ). Remarks. Aegus chelifer was described by Macleay (1819) from “Australasia” without more precise locality. The syntype of Aegus chelifer ( Figs. 45–47 ) is a small size male that does not present the middle tooth on the mandible. There are three junior synonyms of A. chelifer , two of which have been treated as subspecies in some studies. Boileau (1899) described Aegus nitidus from Borneo which he later synonymized to Aegus chelifer ( Boileau, 1913 ) . Subsequently, Mizunuma & Nagai (1994) treated taxon nitidus as a subspecies of Aegus chelifer without any formal status revise or explanatory remark. Another junior synonym, Aegus specularis tonkinensis Kriesche, 1920 from Tonkin , Vietnam , was synonymized as Aegus chelifer by Benesh (1960) . Huang & Chen (2017) illustrated two syntypes of Aegus specularis tonkinensis and revised it to subspecies level of Aegus chelifer without formal status revise. Bomans (1992) later described Aegus chelifer crassodontus from Annam , Vietnam with some of the paratypes from northern Thailand . However, the holotype ( Figs. 48–50 ) shows high similarity to one of the syntypes of A. specularis tonkinensis , by the short-thickness of mandible with the large middle tooth. This character was used by Bomans (1992) to distinguish A. chelifer crassodontus from A. chelifer . Based on the specimens examined from our collection and the series of A. chelifer in Mizunuma & Nagai (1994) and Fujita (2010) these characters are not stable and can be found in the sympatric area with A. chelifer . Overall, the morphological characters of the syntype of Aegus chelifer , the holotype of A. chelifer crassodontus and the syntype of A. specularis tonkinensis can be placed in between the variations of A. chelifer , even within the variation of the populations distributed in Thailand (figs. 1–5; Mizunuma & Nagai, 1994 ; Fujita, 2010 ). The variations of these type specimens can be found to occur in nearby locations with some intermediates between them. There are no stable morphological characters or distinct, separated populations which could be used to discriminate subspecies. Moreover, we have dissected the genitalia of males from several places in Thailand and found no significant difference. In addition, according to Huang and Chen (2017) , subspecific classification of A. chelifer should not be clarified due to the precise type locality being unknown. From the aforementioned reasons, we thereby confirm the synonym status of Aegus nitidus Boileau, 1899 and Aegus specularis tonkinensis Kriesche, 1920 , and treat Aegus chelifer crassodontus Bomans, 1993 as new junior synonym of Aegus chelifer Macleay, 1819 herein.