Revision of Chaetocnema semicoerulea species-group (Coleoptera, Chrysomelidae, Galerucinae, Alticini) in China, with descriptions of three new species

Abstract Chinese species of Chaetocnema semicoerulea group are revised and three new species described as new: Chaetocnema salixis sp. n., Chaetocnema yulongensis sp. n. and Chaetocnema deqinensis sp. n.. A key to all five species of this group occurring in China and the illustrations of habitus and genitalia are provided. A map of species distribution is given.


Introduction
There are more than 400 species of Chaetocnema known in the world (Konstantinov et al. 2011). Approximately 43 species are known to occur in China; however, Chinese Chaetocnema species still remained mostly unknown and need to be collected, properly documented and ultimately revised. The Chinese Chaetocnema picipes species-group has been studied previously (Ruan et al. 2014), and this paper is a second contribution to the revision of Chaetocnema in China.
Chaetocnema semicoerulea species-group is similar to Chaetocnema picipes speciesgroup (Ruan et al. 2014). They share a number of character states, such as: vertex sparsely and unevenly covered with punctures near each eye; frontal ridge narrow and convex; base of pronotum with two short longitudinal impressions; deep row of large punctures at base of pronotum present on sides, lacking in middle. Chaetocnema semicoerulea species-group can be differentiated from picipes species-group by the following character states: apical part of median lobe in ventral view with polygonal line on lateral sides; apex of median lobe in lateral view sinuated.
Species of the semicoerulea species-group usually feed on Salix or Rubus.

Material and methods
Photographic technique, morphological terminology and anatomy method used in Ruan et al. (2014) are followed. Distributional records of species are arranged from north to south. Province names in "Material" paragraphs are in bold.

Chaetocnema semicoerulea species-group
Diagnosis. Body length usually 1.60-3.00 mm. Apex of median lobe narrowing with polygonal line on sides, apical denticle weak or absent; median lobe in lateral view sinuated on apex; spermathecal receptacle pear-shaped, basal part of spermathecal duct straight; frontal ridge narrow and convex; vertex sparsely and unevenly covered with punctures near eyes; all rows of punctures on elytra regular.
In history, many authors erroneously used Tlanoma Motschulsky as a subgenus name in the genus Chaetocnema. This mistake was fully discussed by Konstantinov et al. (2011). They pointed out that C. concinna Marsham is the correct type of genus Chaetocnema designated by Westwood 1838, instead of C. hortensis (Geofrroy) desinated by Maulik (1926) which was erroneously used by many authors in history and recently; the valid name for subgenus should be Chaetocnema (s. str.) (subgeneric type C. concinna) and Udorpes (subgeneric type C. splendens); Tlanoma Motschulsky fact is a subjective junior synonym of Chaetocnema in the strict sense. We agree with their proposal to use Chaetocnema and Udorpes as two valid subgeneric names in the genus Chaetocnema. Based on the narrow and raised frontal ridge and sparse punctures near each eye, species of the semicoerulea group can be classified in the subgenus Chaetocnema (s. str.) Marsham. Although the same paper suggested not to use any subgeneric classification until rigorous phylogenetic analysis has been conducted in this genus, in this study the species group is used for practical reasons.  (Heikertinger 1951), Far East (Bukejs 2008)]; Middle Asia (Heikertinger 1951); Europe (Konstantinov et al. 2011).
Head hypognathous. Frontal ridge between antennal sockets narrow and convex. Frontolateral sulcus present. Orbital sulcus deep. Suprafrontal sulcus relatively deep, well-defined, retuse. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 1.35-1.45. Vertex flat, situated on same level as orbit. Surface of vertex covered with 15-20 punctures next to each eye.
Base of pronotum with two longitudinal impressions. Deep row of large punctures at base of pronotum present on sides, lacking in middle. Pronotal base evenly convex. Sides of pronotum slightly convex with maximum width near base. Anterolateral prothoracic callosity protruding laterally forming a round angle. Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 2-4 times smaller than distance between them.
Elytra with convex sides. All rows of punctures of elytra regular. Elytral humeral callus well-developed. Interspace between stria of punctures on the elytra smooth. Numbers of lines of minute punctures on each interspace: 2-3.
First male protarsomere length to width ratio: 2.20-2.25. First and second male protarsomeres length to length ratio: 1.13-1.19. First and second male protarsomeres width to width ratio: 1.61-1.67. Length of metatibia to distance between denticle and metatibial apex: 2.37-2.45. Large lateral denticle on metatibia sharp. Metatibial serration proximal to large lateral denticle present, sharp. First male metatarsomere length to width ratio: 2.97-3.06. First male protarsomere maximum width to width at base ratio: 2.12-2.19. First and second male metatarsomeres length to length ratio, 1.71-1.78. First and second male metatarsomeres width to width ratio: 1.00-1.06. Third and fourth male metatarsomeres length to length ratio: 1.54-1.59.
Apical part of median lobe narrower than middle. Apical part in ventral view narrowing gradually with polygonal line on sides. Ventral longitudinal groove poorly developed, shallow or absent. Apical and basal parts of longitudinal groove usually subequal in width, wider than middle. Apical denticle in ventral view absent. Minute transverse wrinkles on ventral side present. Median lobe in lateral view sinusoidal near apex with maximal curvature situated medially.
Spermathecal pump attached to middle of receptacle top. Maximum width of receptacle situated at about middle. Basal part of receptacle wider than apical. Posterior sclerotization of tignum spoon shaped, wider than midsection. Midsection of tignum curved. Sides of midpart of vaginal palpus narrowed. Anterior end of anterior sclerotization narrowly rounded. Length of posterior sclerotization greater than width. Width of anterior sclerotization greater than width of posterior sclerotization. Material. 1♂, China, Wuyiling, Yichun, Heilongjiang, 31.VIII.1970 (IZCAS). Remarks. Chaetocnema semicoerulea from the Palearctic Region has been recently revised by Konstantinov et al. (2011). This species is recorded in China for the first time. Only found one male specimen was found in China with all the characters in accordance with the European specimens that are available for study except the reduced body size (2.05 mm in body length). Figure 2 Chaetocnema transbaicalica Heikertinger, 1951: 173  Ratio of pronotum width at base to length at middle: 1.70-1.86. Ratio of length of elytron at suture to length of pronotum at middle: 3.28-3.38. Ratio of width of both elytra at base to width of pronotum at base: 1.07-1.19. Ratio of maximum width of both elytra to maximum width of pronotum: 1.40-1.44.
Head hypognathous. Frontal ridge between antennal sockets narrow and convex. Frontolateral sulcus present. Suprafrontal sulcus shallow and faint, retuse. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 1.30-1.40. Surface of vertex with 8-10 punctures near each eye.
Base of pronotum with two short longitudinal impressions. Deep row of large punctures at base of pronotum present on sides, lacking in middle. Pronotal base evenly convex. Sides of pronotum slightly convex with maximum width near base. Anterolateral prothoracic callosity protruding laterally. Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 2-4 times smaller than distance between them.
Elytra with convex sides. All rows of punctures on elytra regular, scutellar row single. Elytral humeral callus well-developed. First male protarsomere length to width ratio: 1.48-1.51. First male protarsomere maximum width to width at base ratio: 1.98-2.04. First and second male protarsomere length to length ratio: 1.79-1.83. First and second male protarsomeres width to width ratio: 1.06-1.09. Length of metatibia to distance between denticle and metatibial apex: 2.27-2.32. Large lateral denticle on metatibia sharp. Metatibial serration proximal to large lateral denticle present, sharp. First male metatarsomere length to width ratio: 2.96-3.05. First and second male metatarsomeres length to length ratio: 1.30-1.70. First and second male metatarsomeres width to width ratio: 0.85-0.91. Third and fourth male metatarsomeres length to length ratio, 1.63-1.69.
Apical part of median lobe in ventral view narrowing gradually with polygonal line on sides. Apical denticle in ventral view absent. Minute transverse wrinkles on ventral side present. Ventral longitudinal groove poorly developed in apical and basal part, shallow, with obtuse margins; obscure or absent in middle. Apical part of longitudinal groove wider than basal; middle part narrower than basal and apical. Median lobe in lateral view sinusoidal near apex with maximal curvature situated medially.
Spermathecal pump much shorter than receptacle. Apex of spermathecal pump cylindrical. Spermathecal receptacle pear-shaped. Spermathecal pump attached to middle of receptacle top. Maximum width of receptacle situated at about middle.
Basal part of receptacle about as wide as apical. Posterior sclerotization of tignum spatulate, wider than midsection. Apex of vaginal palpus subdeltoid, with sides abruptly tapering. Sides of midpart of vaginal palpus (before apex) narrowing from base, slightly widening towards apex. Anterior sclerotization of vaginal palpus as wide posteriorly as anteriorly before apex; sharply curved at apex. Anterior end of anterior sclerotization broadly rounded or acute. Length of posterior sclerotization greater than width. Width of posterior sclerotization great or greater than width of anterior sclerotization.
Type material. Remarks. Chaetocnema transbaicalica from the Palearctic Region has been recently revised by Konstantinov et al. (2011). This species is previously recorded in Russia and Mongolia. This species is recorded in China for the first time.
Host plants. Salix sp. Distribution. China: Shannxi, Gansu, Sichuang. Diagnosis. Chaetocnema salixis resembles C. transbaicalica. It can be differentiated from the latter by the following characters: frontolateral angle of pronotum long and sharp laterally; both longitudinal groove and transverse wrinkles on ventral surface of median lobe absent; metatibial serration proximal to large lateral denticle absent or obscure.
Head hypognathous. Frontal ridge between antennal sockets narrow and convex. Frontolateral sulcus present. Suprafrontal sulcus deep laterally, absent in middle. Orbital sulcus deep. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 1.20-1.25. Width of frontolateral sulcus to width of antennal socket: 0.29-0.38. Width of orbital sulcus to width of frontolateral sulcus: 0.72. Numbers of punctures on vertex next to each eye: 7-9. Numbers of punctures on orbit: 2. Numbers of hairs along frontolateral sulcus: 9-11. Numbers of hairs on front (triangle area surrounded by frontolateral sulcus and clypeus): 0. Numbers of hairs on clypeus: 8. Numbers of hairs on labrum: 6. Anterior margin of labrum slightly concave in middle.
Base of pronotum with two obscure longitudinal impressions visible only near basal margin. Deep row of large punctures at base of pronotum present on sides, lacking in middle. Pronotal base slightly expanded in middle. Lateral sides of pronotum slightly convex with maximum width near base. Anterolateral prothoracic callosity protruding laterally, forming a sharp angle laterally (Fig. 3: B2). Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 2 to 4 times smaller than distance between them.
Elytra with convex sides. All rows of punctures regular. Elytral humeral callus well developed. Interspace between stria of punctures smooth and glabrous. Numbers of stria of minute punctures on each interspace: 2.
First male protarsomere slightly larger than second one. First male protarsomere, length to width ratio: 1.74-1.78. First and second male protarsomeres, length to length ratio: 1.60-1.80. First and second male protarsomeres, width to width ratio: 1.04-1.20. First male protarsomere, width at apex to width at base: 1.50-1.53. Length of metatibia to distance between denticle and metatibial apex: 2.28-2.36. Large lateral denticle on metatibia sharp. Metatibial serration proximal to large lateral denticle absent or obscure. First male metatarsomere, length to width ratio: 2.80-3.40. First and second male metatarsomeres, length to length ratio: 2.03-2.15. First and second male metatarsomeres, width to width ratio: 0.87-0.97. Third and fourth male metatarsomeres, length to length ratio: 0.52-0.55.
Apical part of median lobe in ventral view narrowing gradually with polygonal line on sides. Ventral longitudinal groove absent. Apical denticle in ventral view absent. Minute transverse wrinkles on ventral side absent. Median lobe in lateral view evenly and strongly curved, slightly sinusoidal near apex. Maximal curvature of median lobe in lateral view situated medially.
Spermathecal receptacle pear-shaped. Basal part of spermatheca duct straight. Spermathecal pump much shorter than receptacle. Apex of spermathecal pump cylin-drical or pointed. Spermathecal pump attached to middle of receptacle top. Basal part of receptacle about as wide as apical. Posterior sclerotization of tignum spoon-shaped, wider than mid section. Mid section of tignum nearly straight. Anterior sclerotization of tignum about as wide as mid section. Apex of vaginal palpus subdeltoid, with lateral side slightly arching. Sides of mid part of vaginal palpus (before apex) narrowing from base, slightly widening towards apex. Anterior sclerotization of vaginal palpus nearly parallel. Anterior end of anterior sclerotization broadly rounded. Length of posterior sclerotization greater than width. Width of posterior sclerotization smaller than width of anterior sclerotization.

Chaetocnema yulongensis
Host plants. Unknown. Distribution. China, Yunnan. Diagnosis. Chaetocnema yulongensis and C. deqinensis are extremely alike externally, but differ significantly in the shape of the median lobe. In C. yulongensis, maximal curvature of the median lobe in lateral view is situated medially; apical end of the median lobe is narrowly rounded; the suprafrontal sulcus is obtuse in the middle. In C. deqinensis, the maximal curvature of the median lobe is situated apically; the apical end of the median lobe is broadly rounded; the superfrontal sulcus is absent in the middle.
Head hypognathous. Frontal ridge between antennal sockets narrow and convex. Frontolateral sulcus present. Orbital sulcus deep. Suprafrontal sulcus deep laterally, Base of pronotum with two obscure longitudinal impressions visible only near basal margin. Deep row of large punctures at base of pronotum present on sides, lacking in middle. Pronotal base evenly convex. Lateral sides of pronotum slightly convex with maximum width near base. Anterolateral prothoracic callosity protruding laterally, forming a round angle fronto-laterally. Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 2 to 4 times smaller than distance between them.
Elytra with convex sides. All rows of punctures regular and single including scutellar row. Elytral humeral callus well developed. Interspaces between stria of punctures smooth and glabrous. Numbers of lines of minute punctures on each interspace: 2.
Apical third of median lobe narrowing with polygonal line on sides. Apical part in ventral view narrowing abruptly. Ventral longitudinal groove absent. Apical denticle in ventral view absent. Minute transverse wrinkles of ventral side absent. Median lobe in lateral view evenly and slightly curved with apex sinuated. Maximal curvature in lateral view situated medially.
Host plants. Duchesnea indica (Andr.) Focke (Rosaceae). Distribution. Guizhou, Yunnan. Diagnosis. Chaetocnema deqinensis resembles C. yulongensis. It can be separated from the latter by the following characters: maximal curvature of median lobe in lateral view situated close to apex; apical end of median lobe broadly rounded; suprafrontal sulcus absent in middle. In C. yulongensis, maximal curvature of median lobe in lateral view situated medially; apical end of median lobe narrowly rounded; suparfrontal sulcus obtuse in middle.
Head hypognathous. Frontal ridge between antennal sockets narrow and convex. Frontolateral sulcus present. Suprafrontal sulcus deep laterally, absent in middle. Orbital sulcus deep. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 1.04-1.07. Width of orbital sulcus to width of frontolateral sulcus: 0.88-0.90. Numbers of punctures on vertex: 8-10. Numbers of punctures on orbit: 4. Numbers of hairs along frontolateral sulcus: 9-10. Numbers of hairs on front (triangle area surrounded by frontolateral sulcus and clypeus): 0. Numbers of hairs on clypeus: 9. Numbers of hairs on labrum: 6. Anterior margin of labrum slightly concave in middle.
Base of pronotum with two obscure longitudinal impressions visible only near basal margin. Deep row of large punctures at base of pronotum present on sides, lacking in middle. Pronotal base evenly convex. Lateral sides of pronotum slightly convex with maximum width near base. Anterolateral prothoracic callosity protruding laterally,