A revision of the Palearctic Ilybius crassus-complex (Coleoptera, Dytiscidae) ANDERS N. NILSSON Nilsson, A.N.: A revision of the Palearctic Ilybius crassas--complex (Coleoptera, Dytiscidae). [En revision av det palearktiska artkomplexet kring dykarbaggen I/y bius crassus (Coleoptera, Dytiscidae).1 - Ent. Tidskr. I l5 (l-2): 55-61. Uppsala, Sweden 1994. ISSN 0013-886x. The three species of the Palearctic llybius crassus complex are revised. A lectotype is designatedof theWestPalearcticspecies/. crassus Thomson, 1856. Ilybiusnakaneisp.n.is described from South Sakhalin and Hokkaido. Ilybius weymarni J.Balfour-Browne, 1947, is made a junior synonym of /. chishimanus Kdno,1944, syn. n. This species is known from East Siberia, Primorye, North Kuril Islands, and Northeast China. Ilybius subaeneus Erichson, 1837, is reported from Mongolia for the first time. A.N. Nilsson, Department of Animal Ecology, University of Umed, S-901 87 Umed, Sweden. Introduction (1989) Ilybius crassus Thomson, 1856, was long regarded redescribed/. weymarni from Sakhalin and Hokkaido, including illustrations male genitalia as a strictly central and northem European species, of providing a scholar example of a boreoalpine dist- evidently different from those of European I. ribution (Holdhaus & Lindroth 1939, Dettner 1977). crassus. The study of a large material from Siberia, Pri- Quite surprisingly,Zaitzev (1953) recorded the spe- and cies from "Siberia to the Far East" (of Russia). Pre- morye, Sakhalin Hokkaido has convinced me the presence three different species the vious to Zaiazev's widening of the range of 1. of of in cras.sus-complex. lrue crassus, KOno ( 19,14) had described /. chishimanus The I. crassus is seemingly from the North Kuril Islands, and Balfour-Browne European, and two species occur in the Far East, which one has to be described as new. As have ( 1947) had described 1. weymarni from Manchuria of I not seen material as being very close to I. crassus. any from West Siberia it is still For a long period the question seemed open an open question which species of the complex, if whether the East Palearctic populations were any, that occurs in this region. conspecific with /. crassas or not. Gu6orguiev ( 1968, 1972) enoneously recorded L crassus from Mon- Abbreviations golia (see below), and Sat6 & Nilsson (1988) The following abbreviations are used for museums synonymized I. chishimanus with 1. crassas. The and other collections cited: (BML) The Natural presence of L crassus in the Far East was also ve- History Museum, London, (CAL) coll. Angus, Lon- rified by Lafer (1989). don, (CNU) coll. Nilsson, UmeA, (CTC) coll. T. The status of l. weymarni has remained unclear, Nakane, Chiba, (NSMT) National Science Museum, and Larson (1987) suggested that it was a junior Tokyo, (SMNH) Swedish Museum of Natural His- synonym of I. crassus. On the other hand, Nakane tory, Stockholm, (TMB) Term6szettudomiinyi 55 Anders N. Ni/sson Ent. Tidskr. ll5 (1994) - Penis in lateral view less strongly tapering to blunt apex (Fig. 7); dorsal groove ending on left side of apex (Fig. 6). Male anterior metatarsal claw apically pointed (Fig. 10). Rugosity of male abdominal sternum 6 present also medially. Metasternal wing relatively broader, WC/IVS 3.0 or less in most spe- cimens.......... nakanei 2. Penis more evenly tapering to apex in lateral view (Fig. 3); dorsal groove not broadly visible subapically when viewed from right side (Fig. 2) K6no, paramere, internal Fig. l. Ilybius chishimanus crassus view. Scale har 0.5 mm. - Penis more abruptly tapering to apex in lateral view (Fig. 5); dorsal groove broadly visible when Hanens paramer sedd frdn insidan. viewed from right side (Fig.4)........ chishimanus Descriptions of species Mrizeum, Budapest, (ZIS) Zoological Institute (Aca- de my of S c ience s ), S t. Pete rsb urg, (ZlY ) Zoolo gical I lybius crassus Thomson Institute (Academy of Sciences), Vladivostok, (ZML) Zoological Museum, Lund. Dytiscus fenestratas Fabricius, l78l: var. c Gyllenhal, 1808:498 (misident.); var. b Zetterstedt, 1828:215 Characterization of the crassus-complex (misident.); vars. b and c Zetterstedt, 1837:l3l (misi- dent.). The following combination of characters separates llybius crossus Thomson, 1856:224 (orig. descr.); Zim- species of the crassas-complex from other Ilybius- merrnann & Gschwendtner 1935:83 (descr.); Holdhaus Characters are given as plesio- (P) or apomorphic & Lindroth 1939:148 (distr.). (A) within the genus using Larson's (1987) polar- ity decisions: (l P) antenna without apical in- Type locality. "Lappland" (Sweden). fuscation, (2 P) body black, (3 A) body with dorsal Type material. Lectotype d here designated in surface aeneous, (4 ?) body of medium size, total coll. Thomson (ZML) labelled: black square, "d", length l0-12.5 mm, (5 A) metastemal wing rela- and my lectotype label. - Paralectotypes 8Cfi9 here tively narrow, (6 A) metacoxal plate with longitu- designated in coll. Zetterstedt (ZML) under dinal strioles frequently intersecting, (7 P) metatibia "Dytiscus fenestratus", all except ld provided with with ventral face punctate, (8 A) male sternum 6 black square and the following additional labels: rugose with posteromedial keel reduced, (9 A) para- ld "Var. b. d.", 19 "Var. b. 9.", ld "Var. c. d.", mere with sucker setae on mesal face (Fig. l), (10 t9 "Var. c.9.", td "Var. d. Yar.b.Zett. Fn. Lapp.", ?) male metatarsomeres 1-3 provided with ventral td "Var. c.Zett.Fn. Lapp. Lycksele" (without black setal fringe, ( I I A) male metatarsomeres 1-4 ridged, square), 1d "65.", "Colymb. fenestratus c. Gyll. a (12 A) male anterior metatarsal claw blade-like with Schcinh. L"pp.", 19 "65. Sch.", and my ventral margin more or less straight, ( 13 A) female paralectotype labels. sternum 6 with marginal bead obsolete on outer Additional material. Forty specimens from angle of medial emargination. northem Sweden in CNU were examined. Notes. Thomson's description of crassus was Key to species of crassus-complex for males based on specimens collected by Zetterstedt in 1. Penis in lateral view more strongly tapering Lapland, i.e. types may be found in both coll. Thom- subapically to blunt apex (Figs 3, 5); dorsal groove son and coll. Zetterstedt. Only one male in coll. ending on right side of apex (Figs 2, 4). Male Thomson can without doubt be connected with anterior metatarsal claw apically truncate (Figs 8- Zetterstedt. This male, selected as lectotype above, 9). Rugosity of male abdominal sternum 6 more is provided with a minute black square, used by strongly reduced medially. Metasternal wing Zetterstedt for the material collected on his 1832 relatively narrower, WCAMS > 3.0 in most speci- expedition to South Lapland (now Ly lpm) (Da- mens..,........... ,,,......2 nielsson in litt.). The five specimens in coll. Thom- 56 Ent. Tidskr. I 15 (1994) T he I ly bius c rass us - complex son seen by Brinck (1942) are not part ofthe type material, and one male belongs to L quadriguttatus (Lacordaire, 1 835). Based on his "Insecta Lapponica" collection (ZML), the Dytiscus fenestratus of Zetterstedt ( 1837) is identical with 1. subaeneus Eichson, I 837, whereas his varieties b and c refer to I. crassus. Seidlitz (1887) and Scholz (1915) both listed /. ovatus Hochhuth, 1871, as ajunior synonyn of1. crassus. However, as shown by Zaitzev (19O8) Hochhuth's name is a junior synonym of I . similis Thomson, 1856. Description. Measurements and ratios as in Table Figs 2-7. Ilybius, penis apex in dorsal view (2, 4, 6) and l. Metasternal wing relatively narrow. Male stemum penis in lateral view (3, 5 ,7 ). -2-3. I. crassus Thomson, 6 with rugosity reduced medially. Male anterior Sweden. -4-5. I. chishinanus K6no, Primorye. -6-7. I. metatarsal claw apically truncate (Fig. 8). Penis nakanei sp. n., Sakhalin. Scale bar 0.5 mm. (Figs 2-3) evenly tapering to rounded apex; dorsal groove ending on right side ofapical knob, invisible Hanens penis sedd frdn sidan (3, 5, 7), resp penis- in lateral view. spetsen sedd uppifrdn (2, 4, 6). Distribution. Central and North Europe east to the Urals. Germany (Dettner 1977, Braasch 1989), Austria (Schaeflein 1989), Poland (Galewski I 966), Czechoslovakia (Riha 1992), Denmark (Holmen I 979), Fennoscandia (Lindroth I 960), Russia. The eastemmost literature records found are from Mezen in the Arkhangelsk Prov. (Poppius 1908), and from Kuznetsk in the Penzensk Prov. (Zaitzev 1928). Moreover, Zailzev (1915) reported on one speci- men in coll. Motschulsky labelled "Ural", conside- redby Zaitzev to originate from the central part. I lybius chishimanus K6no Ilybius ater (De Geer, 1774): Kano 1933:97 (misident.); Kamiya 1935:506 (misident.); Kamiya 1938:40 (in part, misident.). Ilybius crassus Thomson, 1856: Zaitzev 1953:.278 (in part, misident.); Sat6 & Nilsson 1988:126 (misident.); Figs 8-10. Ilybius, male protarsomere 5 with claws, Nakane 1989:28 (misident.); Lafer 1989:249 (in part, anterior view. -8. I. crassus Thomson, Sweden. -9. I. misident.). chishimanus K6no, Primorye. -10. L nakanei sp. n., Ilybius chishimanus K6no, l9M:80 (orig. descr.). Sakhalin. Scale bar 0.2 mm. Ilybius weymarri J.Balfour-Browne, 1947 :446 (orig. descr.), syn. n. Hanens sista baktarssegment med klor sett framifrdn. Type locality: of chishimanns "Suribachi Bay, 40 M. Weymarn", "Ilybius weymami Hototype! J. Paramusir Island" (here translated) (Russia, North Balfour-Browne det.", "Brit. Mus. 1948- 339." Kuril Islands); of weymarni "Manchuria, Kaolint- Paratype 9 in el\4t labelled: "Allotype", "Cheng- su" (China, Heilungkiang Prov.). chin, Lesser Khingan, Manchukuo", "20.VI.38 M. Type material. Holotype Q of chishimanus seen Weymarn", "Brit. Mus. 1948-339", "Ilybius wey- in NSMT. - Holotype d of weymanri in BML la- marni sp.n. J. Balfour-Browne det." belled: "Holotype", "Kaolintsu, Manchuria 20.VIII.- Additional material. Russia: Transbaikalien 1d 57 Anders N. Ni/sson Ent. Tidskr. I l5 (1994) leg. Leder & Reitter (TMB); 45 km S of Irkutsk l 3.viii. l 968 ld29 lel. Lindroth (ZML); Tibelti, Irkut valley, 28 km W of L.