Mulsant (1854) erected Palorus as a subgenus of Hypophloeus to contain Hypophloeus depressus Fabricius. The genus Palorus belonging to tribe Palorini is the largest of the group with thirty-seven known species in Africa, Eurasia and the Pacific (Halstead, 1967) and consists of 11 species in the Palaeartic region (Löbl et al., 2008). Members of genus Palorus are recognized as follows: small beetles, varying from 1.5 to 4.0 mm in length; dorsal margin of eye level with side margin of head (apical region may be concealed dorsally by gena), usually distinctly margined by a supra-orbital carina; front of head flat or raised; elytra with interstitial punctures usually much finer than strial punctures, elytra not carinate. The majority live under the bark of trees or in the galleries of wood-boring beetles, but two species, Palorus ratzeburgii (Wissmann) and Palorus subdepressus (Wollaston) are commonly found in stored food products, and Palorus genalis Blair, P. cerylonoides (Pascoe), P. ficicola (Woolaston) and P. laesicollis (Fairmaire) are found there also, but less frequently (Halstead, 1967).

In this paper, we report two cosmopolitan stored product pests by Palorus subdepressus (Wollaston) and Palorus ratzeburgii (Wissmann) for the first time from Korea. Morphological photographs of adults, diagnosis and illustrations of diagnostic characters, and taxonomic key to the 6 species related to inspection for plant quarantine on stored products in Korea are provided.

Materials and Methods

Materials for this study were collected in rice mills and are deposited in the Insect Collection of Sunchon National University.

The following abbreviations are used in this paper: CB, Chungcheongbuk-do Province; GB, Gyeongsangbuk-do Province; GG, Gyeonggi-do Province; CN, Chungcheongnam-do Province; JJ, Jeju-do Island; JN, Jellanam-do Province, Korea; SCNU, Sunchon National University, Suncheon, Korea.

Results and Discussion

Taxonomic accounts

Tribe Palorini Matthews, 2003

Genus PalorusMulsant, 1854 쌀도둑거저리속(신칭)

PalorusMulsant, 1854: 250.

Caenocorse C.G. Thomson, 1859: 117.

EbaPascoe, 1863: 129.

PlatyotusGerstaecker, 1871: 62.

CircomusFleischer, 1900: 236.

StenopalorusBlair, 1930: 136.

Type species: Hypophloeus depressus Fabricius, 1790

Palorus ratzeburgii (Wissmann, 1848) 넓은이마쌀도둑거저리 (신칭) (Figs. 1, 3A-B)

Hypophloeus ratzeburgiiWissmann, 1848: 77.

Hypophloeus ambiguus Wollaston, 1857: 152.

Hypophloeus floricolaMarseul, 1876: 115.

Caenocorse galilaeus J.R. Sahlberg, 1913: 49.

Body length 2.5-2.8 mm, width 0.9-1.1 mm, brown to dark brown, weakly shining, microreticulation distinct. Head moderately densely punctured; genae not produced or raised, almost level with clypeus, slightly raised above antennal insertions, puncturation a little finer than that of vertex; clypeus raised medially, puncturation similar to genal puncturation; eyes small, dorsal length equal to or less than width of scutellum; supra-orbital carinae very strongly developed. A pressed flat area at anterior margin of head broader than its outer margin and its margin in front of eye distinctly produced with eyeshade-like form.

Pronotum usually widest near apex but sometimes with sides more parallel; punctures not bearing distinct setae, small on disc, separated by 4-5 diamenters, coarser laterally, separated by 1-2 diameters; usually shining. Elytra with scutellary striole represented by five or less, ill-defined punctures; interstices with single rows of punctures.

Specimens examined: [SCNU] GG 13 exs., Duchang rice mill (rice hull), Duchang-ri Wonsam-myeon Yongin-si, 19 Ⅷ, 2004, I.S. Kim; CB 1 ex., rice mill (rice hull), Goesan-gun, 14 Ⅵ 2004, I.S. Kim; JN 5 exs., Jangseong (rice bran), 6 Ⅶ, 2004, I.S. Kim; 5 exs., Samjeong rice mill, Samjeon-ri Okryong-myeon Gwangywang-si, 25 Ⅶ 2013, K.J Hong; GB 5 exs., Gumi rice mill, Gumi-ri Guseong-myeon Gimcheon-si (N360043 E1280152), 10 XI 2013, K.J. Hong; 2 exs., Naeseong rice mill, Naeseong-ri Bonghwa-eub Bonghwa-gun (N365313 E1284427), 10 XI 2013, K.J. Hong; JJ 2 exs., Warehouse (rice), Hangyeongmyeon Bukjeju-gun, 24 IXX 1998, K.J. Hong.

Distribution. Korea (new record), Cosmopolitan.

Biological notes. The under bark habitat is apparently the natural one. This species spread to all parts of the world by commerce, occurs as a secondary pest in granaries, warehouses, flour mills etc., where it is found in cereals and cereal products (Halstead, 1967). This species was collected from several rice mills in the Korean peninsula including Jeju island. It is associated with other pests, particularly the maize weevil, Sitophilus zeamais Motschulsky.

Palorus subdepressus (Wollaston, 1864) 좁은이마쌀도둑거저리 (신칭) (Figs. 2, 3C-D)

Hypophloeus subdepressus Wollaston, 1864: 499.

Palorus bifoveolatusBaudi di Selve, 1876: 235.

Body length 2.7-3.0 mm, width 0.9-1.0 mm, red-brown, moderately shining; microreticulation shallow but usually distinct. Head usually with more or less distinct shallow median depression towards base; genae raised above clypeus, developed to a greater or lesser extent independently of sex or head size, posteriorly produced backwards covering apical region of eyes to a variable extent and continuous in a straight line with supraorbital carinae; eyes variable in size, separated ventrally by 2.7-4.1 diameters. A pressed flat area at anterior margin of head narrower than its outer margin and its margin in front of eye not produced.

Pronotum transverse, sides slightly rounded to almost parallel; larger specimens sometimes with very shallow, ill-defined, lateral longitudinal depressions; a very small impunctate region on either side on basal half is often present. Mesosternum usually with coarse, rarely rugose but not longitudinally rugose, puncturation. Elytra very slightly depressed.

Specimens examined: CN 6 exs., rice mill (rice bran), Nonsan-si, 6 Ⅶ 2004, I.S. Kim.

Distribution. Korea (new record – Central), Cosmopolitan.

Biological notes. This species probably originated in Africa. The under bark habitat must be the natural one. This species is a secondary pest frequently associated with the grain weevil, Sitophilus, most frequently recorded on cereals and cereal products and also sometimes on other commodities ginger, groundnuts, copra, illipe nuts etc (Halstead, 1967).

Remarks. We have examined only one site which collected by I.S. Kim on July 6, 2004 from a rice mill at Nonsan city of Chungnam province in Korea. In 2013, we visited at this collecting site for gathering more specimens but, could not found the rice mill because probably wound up this business. On the other hand, this species has been designated as a quarantine pest on the Plant Protection Act in Korea. Therefore, it should be needed to survey on this species nationwide in order to the Pest Risk Analysis for exception from the list of quarantine pests.

Key to the 6 species of the the genus Palorus for the inspection of plant quarantine in Korea

The genus Palorus contains thirty-seven known species in the world (Halstead, 1967). The majority live under the bark of trees or in the galleries of wood-boring beetles, but some species are related to stored food products and have an economic importance on the international commerce (Table 1). Key to these 6 species related to stored food products as followed (modified from Halstead, 1967);