Taxonomic history

Xyleborus protensus Eggers, 1930: 201. 

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

Synonyms

Cnestus rostratus Schedl, 1977: 502. Smith et al. 2020b: 151.

Diagnosis

3.3−5.4 mm long (mean = 4.35 mm; n = 4); 2.0− 2.17 times as long as wide. This species can be 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 shining; elytral declivity strongly rounded; protibia very slender with three large, narrow denticles on outer margin; antennal club type 1, with no sutures visible on the posterior face; and three segmented antennal funicle.

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

May be confused with

Cnestus nitidipennis

Distribution

China (Yunnan), India (Assam), Indonesia (Java), Laos, Thailand, Vietnam

Host plants

recorded from Machilus (Lauraceae) (Smith et al. 2020b)

Remarks

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 domicile parasites of other ambrosia beetles such as Sampsonius Eggers, 1935 (Xyleborini) and Amphicranus Erichson, 1836 (Corthylini) (Wood 2007). Further investigation of their behavior in is necessary to determine if these species are also domicile parasites.

DNA data

specimens not available for sequencing