Xyleborinus exiguus (Walker, 1859)

Smith, Sarah M., Beaver, Roger A. & Cognato, Anthony I., 2020, A monograph of the Xyleborini (Coleoptera, Curculionidae, Scolytinae) of the Indochinese Peninsula (except Malaysia) and China, ZooKeys 983, pp. 1-442 : 1

Xyleborinus exiguus (Walker, 1859) Fig. 83G, H, L

Bostrichus exiguus Walker, 1859: 260.

Xyleborinus exiguus (Walker): Maiti and Saha 1986: 109.

Xyleborus muriceus Eichhoff, 1878a: 392. Synonymy: Eggers 1925: 154.

Xyleborus diversus Schedl, 1954b: 80. syn. nov.

Xyleborus perexiguus Schedl, 1971b: 381. Synonymy: Hulcr and Cognato 2013: 142.

Xyleborus ankius Schedl, 1975c: 361. Synonymy: Hulcr and Cognato 2013: 142.

Type material.

Holotype Bostrichus exiguus (NHMUK). Paralectotype Xyleborus diversus (NHMUK). The holotype of Xyleborus muriceus was destroyed in the bombing of UHZM in World War II ( Wood and Bright 1992).

New records.

Cambodia: Kumpong Speu, Oral mountain foot, Cardamom [Mts.], 25-31.i.2006, Oul Yothin, Malaise trap (IRSNB, 1). China: Jiangxi, Shang Rao, 31.viii.2016, Lv-Jia, Lai, S-C., ex Prunus sp. (RABC, 1). S Yunnan, Xishuangbanna, 20 km NW Jinghong, vic. Man Dian (NNNR), 22°07.80'N, 100°40.05'E, 740 m, rubber plantation., 10.x.2008, A. Weigel (RABC, 1); as previous except: 23 km NW Jinghong, vic. Na Ban village (NNNR), 22°10'N, 100°39'E, 700-1000 m, v-vii. 2009, L. Meng (NKME, 10; RABC, 3). Laos: Vientiane, Ban Van Eue, 30.ii.1965 (BPBM, 1). Taiwan: Nantou, Sun Moon Lake, 29.xii.2012, Lin, C-S. (CSLC, 1). Vietnam: Dong Nai, Cat Tien N.P., 11.40817, 107.38098, 134 m, 20-22.ii.2017, VN81, A.I. Cognato, T.A. Hoang, ex FIT (MSUC, 2).

Diagnosis.

1.8-2.0 mm long (mean = 1.88 mm; n = 5); 2.57-3.0 × as long as wide. This species is distinguished by the declivital face with interstriae 2 unarmed by tubercles; elytral apex attenuated, with three (usually) pairs of large flattened tubercles; and declivital interstriae flat, interstriae 2 not impressed.

Similar species.

Xyleborinus huifenyinae , X. perpusillus , X. tritus .

Distribution.

Recorded in the study region from India (Andaman Is), Cambodia*, China* (Jiangxi, Yunnan), Laos*, Myanmar, Nepal, Taiwan*, Thailand, Vietnam. Also recorded from American Samoa, Australia, Cook Is, Federated States of Micronesia, Fiji, Guam, Indonesia (Java, Maluku, Sulawesi, Sumatra), East & West Malaysia, Mariana Is., New Guinea, Niue I., Philippines, Samoa, Solomon Islands, Tahiti. Introduced to West Africa (Angola, Congo, Equatorial Guinea, Gabon, Ghana, Ivory Coast) ( Beaver 2005, Wood and Bright 1992) and Central America (Costa Rica, Panama) ( Kirkendall and Ødegaard 2007).

Host plants.

Polyphagous ( Browne 1961b).

Remarks.

A paralectotype of the West African species, Xyleborus diversus (NHMUK), has been compared directly with the holotype of the Oriental species, Xyleborinus exiguus (NHMUK), and is clearly conspecific. X. diversus is here placed in synonymy with X. exiguus . Kalshoven (1959b) gives details of brood sizes in various hosts in relation to the size of the brood chamber.

Figures

Figure 83. Dorsal, lateral and declivital view of Xyleborinus disgregus holotype, 1.8 - 2.0 mm (A, B, I), X. echinopterus holotype, 3.0 mm (C, D, J), X. ephialtodes holotype, 2.6 mm (E, F, K), and X. exiguus, 1.8 - 2.0 mm (G, H, L).