Cnestus protensus (Eggers, 1930)

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

Cnestus protensus (Eggers, 1930) Fig. 33G, H, L

Xyleborus protensus Eggers, 1930: 201.

Cnestus protensus (Eggers): Wood and Bright 1992: 803.

Cnestus rostratus Schedl, 1977: 502. syn. nov.

Type material.

Holotype Xyleborus protensus (FRI). Holotype Cnestus rostratus (NHMW).

New records.

China: Fujian, Chong’an, Guidun, 950 m, 25.vi.1979, Fusheng Huang, ex Machilus thunbergii (NMNH, 1) as previous except: 1000 m, 8.v.1978, Fusheng Huang, ex evergreen broadleaf tree (NMNH, 1). Yunnan, Sutian, 2014, Tian-Shang (RABC, 3); S. Yunnan, 28 km NW Jinghong, vic. An Ma Xi Zhan (NNNR), 22°12'N, 100°38'E, 700 m, forest, EKL, 28.vi.2008, A. Weigel (RABC, 1). India: Arunachal Pradesh, Etalin vicinity, 28°36'56"N, 95°53'21"E, 700 m, 12-25.v.2012, L. Dembický (ZFMK, 1). Laos: Hua Phan, Ban Saluei, Phou Pan (Mt.), 20°12'N, 104°01'E, 1300-1900 m, 7.iv-25.v.2010, C. Holzschuh (RABC, 1).

Diagnosis.

3.3-5.4 mm long (mean = 4.35 mm; n = 4); 2.0-2.17 × as long as wide. This species is distinguished by the uniquely emarginate epistomal margin; enlarged mandibles (in lateral view protruding forward at 90° to the plane of the frons, dorsoventrally deeper than normal; in anterior view, with an upwardly directed, smooth, rounded process on the dorsal side); absence of a mesonotal mycangial tuft on the pronotal base; pronotum from dorsal view type 6; pronotum apex strongly produced, extending to a process with numerous serrations; body glabrous, strongly shiny; declivity strongly rounded; protibiae very slender with three large, narrow denticles on outer margin; antennal club type 1, with no sutures visible on the posterior face; and 3-segmented antennal funicle.

This species is very similar to C. nitidipennis and is distinguished by the larger size, pronotal base with punctures clearly coarser, denser, surface mostly dull, pronotum appearing wider, sides of pronotum parallel for approximately 1/2 of the total length.

Similar species.

Cnestus nitidipennis .

Distribution.

China* (Yunnan*), India (Assam), Indonesia (Java), Laos*, Vietnam.

Host plants.

This species has only been recorded from Machilus ( Lauraceae ).

Remarks.

Images of the Xyleborus protensus holotype and the holotype of C. rostratus were compared. Though the two specimens differ in size (3.5 and 4.2 mm, respectively) they were clearly conspecific and C. rostratus is here placed in synonymy.

Both C. nitidipennis and C. protensus possess unique morphology among Cnestus species including the pronotal apex very strongly produced, very slender protibia, enlarged mandibles and absence of a mycangial tuft. These morphological characters are convergent with Neotropical genera that are inquilines (see remarks of C. nitidpennis ). Further investigation of their behavior is necessary to determine if these species are also inquilines.

Figures

Figure 33. Dorsal, lateral and declivital view of Cnestus improcerus, 2.7 - 3.3 mm (A, B, I), C. mutilatus, 3.6 - 3.8 mm (C, D, J), C. nitidipennis, 2.8 - 3.2 mm (E, F, K), and C. protensus, 3.3 - 5.4 mm (G, H, L).