Review of the Patrus landaisi species group from Thailand with description of three new species (Coleoptera, Gyrinidae) Author Suksai, Benjamart 0000-0002-2472-6100 benjamartbenjamart@gmail.com Author Gustafson, Grey T. Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA. & Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, 86011, USA. Author Sites, Robert W. 0000-0002-3895-813X Enns Entomology Museum, Division of Plant Science, University of Missouri-Columbia, Missouri 65211, USA. SitesR @ missouri. edu; https: // orcid. org / 0000 - 0002 - 3895 - 813 X Author Sangpradub, Narumon 0000-0002-2472-6100 Applied Taxonomic Research Center, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand & Corresponding Author: narumon @ kku. ac. th; https: // orcid. org / 0000 - 0003 - 0228 - 8696 benjamartbenjamart@gmail.com text Zootaxa 2021 2021-06-25 4991 3 561 591 journal article 10.11646/zootaxa.4991.3.8 1175-5326 5042656 F0FAE07E-4A90-4602-BCC5-6D80E158BB6C Patrus apicalis ( Régimbart, 1891 ) ( Figs. 2A , 3A , 4A , 5 , 13B , 14A ) Orectochilus apicalis Régimbart, 1891: 548 (original description) Orectochilus ( Patrus ) apicalis Régimbart, 1891 : Ochs 1930: 20 Type locality. Karen Hills , Myanmar . Type material examined. HOLOTYPE female ‘Carin / Asciui Ghecù / 1200–1400 m . / L.Fea III–88 [beige label, handwritten black ink]’ MSNG Holotype DSCN0243. Additional label information not provided to authors. Other material examined. THAILAND : Chiang Mai Province : Mae Kam Pong Stream , Huay Kaew Subdistrict , Mae On District , 18°51’58.3”N 99°21’09.4”E , 1011 m a.s.l. , 15.V.2017 , leg. B. Suksai , C. Jaitamart & T. Paotajai , 1 male ( THNHM ) . Chiang Rai Province : Nam Kuen Stream , Ban Huai Nam Kuen , Mae Chedi Subdistrict , Wiang Pa Pao District , 19°07’22.3”N 99°19’43.3”E , 1327 m a.s.l. , 25.V.2017 , leg. P. Sapewisut , 3 males , 3 females ( KKU ) ; same locality except for, 11.XI.2018 , leg. B. Suksai , P. Sapewisut & S. Kullasoot , 4 males , 7 females ( GTGC , KKU , THNHM , UMC ) ; same locality except for, 3.V.2019 , leg. B. Suksai , P. Sapewisut & N. Plangklang , 1 male ( THNHM ) , 4 females ( THNHM , GTGC ) . Nan Province : Khun Sathan Natl. Park. , Ban Mueng Li , Mueng Li Subdistrict , Na Muen District , 18°15’08.44”N 100°29’35.77”E , 786 m a.s.l. , 29.V.2017 , leg. P. Sapewisut , 1 male ( THNHM ) ; Mae Charim Natl. Park. , Huay Nampangyaekkwar , Mae Charim Subdistrict , Mae Charim District , 18°48’46.58”N 101°04’10.21”E , 461 m a.s.l. , 3.I.2013 , leg. K. Rattanachan , 3 females ( NHMW ) . Diagnosis. Size: Male: 13.0–14.0 mm, female: 10.0– 10.9 mm ; body form in lateral view weakly dorsoventrally convex; elytral glabrous region of male ( Figs. 2A , 5A ) cordiform, along suture extending ca. 7/9 length of elytra, laterally expanded in anterior 2/3 to considerably wider than pronotal glabrous region, posterior 1/3 strongly acuminate with rounded margins; female elytral glabrous region ( Figs. 3A , 5E ) dissimilar to male, broad for nearentire length occupying 10/11 elytral width, lateral margins nearly-straight for 3/4 length creating parallel-sided appearance, abruptly acuminate medially in posterior 1/4, posterolateral corners produced into points, posterior margin evenly convex toward suture; in lateral view width of pubescent margin at humeral region nearly equal to that extending posterior; elytral apex of both sexes similar, obliquely truncate without apicolateral sinuation, epipleural angle distinct, weakly rounded; male protibia wedge-shaped ( Fig. 4A ), without basal constriction, protibial apex obliquely truncate with or without prominent distolateral angle; male protarsus ca. 3/4 length of protibia ( Fig. 4A ), protarsomeres 1–4 mostly similar in width; mesoventrite of male with medial pit; aedeagus ( Fig. 5B–D ) with median lobe in basal 2/3 weakly tapered, weakly constricted medially, parallel-sided in apical 1/3 before acumination, apex strongly constricted to a needle-like point extending 1/5 length, very weakly constricted in lateral view ( Fig. 5C ); female reproductive tract ( Fig. 5G ) without additional sclerotized structure between gonocoxae ( Fig. 5F ), fertilization duct as in Fig. 5H . Differential diagnosis . Patrus apicalis is most similar to P. subapicalis , as the latter was previously considered to be a subspecies of the former. P. apicalis can be distinguished by the mesoventrite of the male having a medial pit, which is absent in both sexes of P. subapicalis . Males of these two species can be also distinguished by the shape of the median lobe of the aedeagus, which in P. apicalis has the apex with a more needle-like point ( Fig. 5B ), compared to P. subapicalis in which the apex is relatively less constricted and has a triangular tip ( Fig. 12B ). Females of both species are similar, but can be separated by the shape of the elytral glabrous region, wherein the lateral margin in P. apicalis appears more rounded for 3/4 of its length ( Fig. 5E ), compared to that of P. subapicalis ( Fig. 12E ) which has a nearly straight lateral margin that creates a more parallel-sided appearance to the elytral glabrous region. The posterior margin of the elytral glabrous region further differs between the two species, having a greater concavity in P. apicalis ( Fig. 5E ) relative to P. subapicalis ( Fig. 12E ). The female of P. apicalis is also similar to that of P. nanensis sp. nov. but can be separated from the latter by the posterior margin of the elytral glabrous region being more rounded in appearance ( Fig. 5E ) compared to P. nanensis sp. nov. which has the posterior margin with a more oblique and angular appearance to its convexity ( Fig. 9E ). Distribution. Previously known from the Karen Hills region of Myanmar and northern Laos ( Peschet 1923 ), this species is here recorded from Thailand for the first time. Within Thailand , it can be collected in slow recesses of high elevation streams ( Fig. 13B ) across the northwestern mountains ( Fig. 14A ). This species has been found together with P. salvazai in streams in Chiang Rai Province ( Fig. 13B ).