Additions to the review of Chinese Enochrus, with description of a new species (Coleoptera, Hydrophilidae, Enochrinae)

Abstract A new species, Enochrus (Methydrus) limbourgi sp. n., is described from Jiangxi Province, Southeast China, and illustrated. Subgenus Enochrus s. str. Thomson, 1859 is recorded for the first time in China, based on the record of Enochrus (s. str.) melanocephalus (Olivier, 1792) from Inner Mongolia. The male of Enochrus (Hydatotrephis) liangi Jia & Zhao, 2007 is described for the first time.


Introduction
revised all species of Enochrus known from China except E. hybridus Hebauer, 2005. Of six subgenera of Enochrus Thomson, 1859, four have been reported from China: Methydrus Rey, 1885, Holcophilydrus Kniz, 1911, Hydatotrephis MacLeay, 1871, and Lumetus Zaitzev, 1908(Hansen 1999, Jia and Zhao 2007, Short and Hebauer 2006, Short and Fikáček 2011. However, the subgenus Enochrus Thomson, 1859 which is reported from Nearctic, Afrotropical, Oriental and Palearctic Regions, has not been recorded to China up to now. In 2013, Enochrus algarum Jia & Short, 2013 was described from Eastern China. The species was not assigned to any subgenus because of a few special characters that do not match any known subgenus. In total, 21 species of Enochrus have now been reported from China. Enochrus (Hydatotrephis) liangi Jia & Zhao, 2007, the sole species of the subgenus occurring in China, was described based on a single female (holotype) from Guizhou Province, China (Jia and Zhao 2007) and it was redescribed in English in detail in 2010 based on the same specimen (Jia and Wang 2010). Unfortunately, male has remained unknown.
In 2014, we have examined some new freshly collected material of Enochrus from various parts of China. Among those, we discovered a male belonging to yet undescribed species from Jiangxi Province, a series of E. liangi including males, and a male specimen of Enochrus s. str. from Inner Mongolia. All these new findings are summarized in this paper, including the description of the new species. Based on the results, we may confirm that all subgenera of Enochrus except Hugoscottia Knish, 1922 (endemic to the Neotropical Region and not likely to be discovered in China) do occur in China.

Material and methods
The holotype and some of the paratypes were dissected and the male genitalia mounted in glycerine on transparent plastic labels attached below each specimen. Specimens and genitalia were examined with the use of an Olympus SZX10 compound microscope. Habitus photographs were taken with ZEISS Axio Cam HRC, Discovery V20. Aedeagus photographs were taken with an Axioskop 40. The photographs were stacked using Auto-Montage software.
Examined specimens are deposited in the following collections: Diagnosis. Head with large preocular spots, reaching frontoclypeal suture posteriorly and reaching inner margin of eyes inwards (Fig. 9), sometimes each preocular spot separated into two spots by a black patch (Fig. 7), or preocular spots connected medially (Fig. 8). Elytron black with posterior half yellow, and yellow colour extends anteriorly as broad band along the lateral margin (Figs 1, 10). Maxillary palps yellow, not dark apically, subequal to the width of head anterior to eyes (Fig. 6). Elytron with a short series of punctures in front of sutural stria, which are same size as other serial punctures (Fig. 10). Fifth abdominal ventrite with apical emargination fringed with stiff yellowish setae (Fig. 11). Aedeagus similar to Enochrus (Methydrus) japonicus (Sharp, 1873) ( Fig. 19), with parameres curved outwards apically, median lobe narrow with sharp apex (Fig. 18). The colour is very similar to Enochrus (Holcophilydrus) laoticus Hebauer, 2005 and the latter also with parameres curved outwards subapically. However, E. laoticus Hebauer with 10 elytral series of punctures; mesosternal process conical, not depressed laterally; median lobe of aedeagus broader and with small emargination apically, as long as parameres.
Description of male. External morphology identical with female. Male genitalia: phallobase slightly longer than parameres. Parameres broad, longer than median lobe, obliquely truncated inwards and strongly bent outwards apically. Median lobe narrower than parameres, gradually narrowed from base to apex, sharp apically (Fig. 18).
Habitat. The series from Jiangxi was collected at margin of natural pools with mud sediment and sparse grass. Lots of E. japonicus (Sharp) were also collected in the same pool. Diagnosis. Size 7.3 mm. Head without preocular spots (Fig. 3). Second maxillary palpomere pronouncedly and extensively darkened except extremity, apical palpomere yellowish brown, not dark apically (Fig. 12). Prosternum with a low carina medially (Fig.  14). Head, pronotum and elytron with fine and very dense punctures (Fig. 13). Scutellum with a few coarse and strong punctures. Claws of anterior and middle legs in male distinctly strongly and angularly curved, bearing a smaller basal tooth. Fifth abdominal ventrite with apical emargination fringed with stiff yellowish setae (Fig. 15). Aedeagus  with parameres curved outwards apically. Median lobe oval broadened basally, abruptly narrowed ca. half, apical half much narrower than parameres, sharp apically (Fig. 20) The new species is most similar to E. (Methydrus) eubenangeei Watts, 1998 which is endemic species to Australia in its large size, black color, punctures on dorsal surface, mesoclaws thickened basally and bent in male, median lobe of aedeagus oval, broadened basally, parameres obliquely truncate apically. In contrast to E. eubenangeei Watts, E. limbourgi is characterized by: pronotum and elytron with distinct pale yellow-brown margin; prosternum with a low distinct median carina; elytra with five series of punctures; claws of male middle tarsi bent, broadly thickened basally; aedeagus with parameres broad, obliquely truncate apically and weakly curved outwards subapically (parameres similar to E. (Methydrus) aliciae Watts, 1998 in form).
The size of this species is the largest in the known species of Enochrus (Methydrus) from the Oriental and southern Palearctic Regions. The median lobe of aedeagus is clearly different from other known Asian species. It is very easy to distinguish this species from other species in Asia by size, punctures and aedeagus. Compared with Chinese species, it is closed to E. japonicus Sharp by size and colour. It can easily be distinguished from the latter by pronotum and elytra with denser ground punctures, serial punctures on elytra less strong and less coarse, mesosternal process strongly depressed laterally, median lobe of aedeagus oval broadened basally, parameres sharp apically.
Head. Antennae with scape ca. as long as antennomeres 2-3 combined. Maxillary palps subequal to the width of head anterior to eyes; apical palpomere about threequarters of penultimate in length (Fig. 12). Anterior margin of clypeus straight medially. Labrum with a median row of setiferous systematic punctures, distinctly coarser than the surrounding ground punctation. Frons and clypeus with ground punctation dense and coarse, distance between ground punctures 1.0-1.2× the width of one puncture; setiferous systematic punctures well pronounced, ca. 3× as large as ground punctures. Mentum subquadrate, with anterior margin slightly depressed medially, not emarginate anteriorly (Fig. 4), ground punctures moderately coarse.
Thorax. Ground punctation on pronotum and elytron similar to that on head, distance between ground punctures 1.0-1.2× the width of one puncture. Elytron with five rows of serial punctures (including lateral series) clearly larger than surrounding ground punctation; without short series of punctures in front of sutural stria, the third series with a few punctures that are distant between punctures. Sutural stria present in posterior half of elytra. Prosternum not tectiform, with a low distinct median carina (Fig. 14) and a transverse groove behind anterior margin. Mesoventrite with a median process which is strongly impressed laterally and with a backwardly pointing projection, rising to level of mesocoxae, apex of the projection with a few long setae. Metaventrite with a very indistinct elongate oval glabrous area posteromedially, longer than wide; glabrous area slightly more than half the total length of the metaventrite. Mesofemora densely pubescent except in apical fifth (Fig. 15). Metafemora with pubescence as in mesofemora (Fig.  15). Posterior tarsomeres with a fringe of long swimming-hairs dorsally. Anterior claws in male strongly and angularly curved, bearing smaller basal tooth; claws of male middle tarsi of similar shape as those of anterior tarsi, but slightly weakly angularly curved; posterior claws only slightly curved , without basal tooth.
Etymology. The specific name is after Dr. Pol Limbourg, an entomologist in Intitute Royal des Sciences Naturelles, Brussels, Belgium, who helped us a lot when senior author studied types of Enochrus in d'Orchymont's collection in Brussels.
Distribution. China (Jiangxi), known only from the type locality.
Habitat. The holotype was collected by light trap.

New faunistic record
Enochrus ( Distribution. This is a widespread species in Europe. It is distributed "from France and the British Isles to Asia Minor" (Hansen 1987). It is only known in Algeria (Hansen, 1999) in Africa and in Israel and Uzbekistan in Asia (Hansen 1999;Hendrich and Hendrich 2005). It is very possible that this species should be distributed in Mongolia and Middle Asia. New for China.

Update of the key to Chinese Enochrus
The key to the species of genus Enochrus of China published by Jia and Wang (2010) should be modified as follows, in order to include E. limbourgi sp. n. and E. melanocephalus recorded as new to China here, and E. algarum described by Jia and Short (2013)