Taxonomic history

Xyleborus subgranulatus Eggers, 1930: 202.

Xyleborinus subgranulatus (Eggers): Wood and Bright, 1992: 817. 

Diagnosis

1.6−1.8 mm long (mean = 1.7 mm; n = 5); 3.0−3.4 times as long as wide. This species is distinguished by the declivital face with interstriae 2 armed by granules at declivital summit, unarmed on declivital face; declivital interstriae 1, 3 denticles subacutely pointed; denticles on ventrolateral areas of the elytra small, less acute; declivital interstriae 2 slightly impressed; discal interstriae 1, 2 minutely granulate, granules extending from declivital summit to mid point of disc; declivital interstriae 2 flattened; and minute size.

The declivital armiture of interstriae 1 is quite variable and specimens of the type series are often exhibit different patterns on each elytron. Denticles may or may not be present on interstriae 1.  

May be confused with

Xyleborinus attenuatus, X. saxesenii, X. subspinosus, and X. thaiphami

Distribution

China (Yunnan), India (Assam, West Bengal), Laos, Taiwan, Thailand, Vietnam

Host plants

recorded from four genera in four different families (Maiti and Saha 2004) as well as Pinus (Pinaceae) and presumably polyphagous (Smith et al. 2020b)

Remarks

This species is strikingly similar to, and has been recovered as sister to Xy. saxesenii using COI data (Cognato et al. 2020b) but the elytral morphology is inconsistent within single specimens. Given its close relationship with X. saxesenii the species is expected to have denticles along declivital interstriae 1 and 3. However this is not always the case and the species can also have declivital interstriae 1 and 2 unarmed with denticles along interstriae 3. Both tubercle patterns have been found on each elytron of single individuals, including the paratype examined and individuals from a series collected in Bengal.

DNA data

Sequences available for COI and CAD.

COI: MN620029

CAD: MN620297