Xyleborinus subgranulatus

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 declivitaldeclivital:
pertaining to the elytral declivity
face with interstriaeinterstria:
longitudinal spaces along the elytra between the striae, which is not as<br /> impressed and bear smaller punctures.
2 armed by granulesgranule:
a small rounded protuberance, like grains of sand
at declivitaldeclivital:
pertaining to the elytral declivity
summit, unarmed on declivitaldeclivital:
pertaining to the elytral declivity
face; declivitaldeclivital:
pertaining to the elytral declivity
interstriae 1, 3 denticlesdenticle:
a small tooth, the sides of which are equal and the tip is above the middle of the base
subacutely pointed; denticlesdenticle:
a small tooth, the sides of which are equal and the tip is above the middle of the base
on ventrolateral areas of the elytraelytron:
the two sclerotized forewings of beetles that protect and cover the flight wings
small, less acute; declivitaldeclivital:
pertaining to the elytral declivity
interstriae 2 slightly impressedimpressed:
a depression in a surface
; discaldiscal:
pertaining to the disc of either the pronotum or elytra
interstriae 1, 2 minutely granulategranulate:
pertaining to a coarse, grainy surface texture
, granulesgranule:
a small rounded protuberance, like grains of sand
extending from declivitaldeclivital:
pertaining to the elytral declivity
summit to mid point of discdisc:
the flat central upper surface of any body part (e.g. pronotum and elytra)
; declivitaldeclivital:
pertaining to the elytral declivity
interstriae 2 flattened; and minute size.

The declivitaldeclivital:
pertaining to the elytral declivity
armiture of interstriaeinterstria:
longitudinal spaces along the elytra between the striae, which is not as<br /> impressed and bear smaller punctures.
1 is quite variable and specimens of the type series are often exhibit different patterns on each elytronelytron:
the two sclerotized forewings of beetles that protect and cover the flight wings
. DenticlesDenticle:
a small tooth, the sides of which are equal and the tip is above the middle of the base
may or may not be present on interstriaeinterstria:
longitudinal spaces along the elytra between the striae, which is not as<br /> impressed and bear smaller punctures.
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 2004Maiti and Saha 2004:
Maiti PK, Saha N. 2004. Fauna of India and the adjacent countries. Scolytidae: Coleoptera (bark and ambrosia beetles). Vol. 1. Part 1. Zoological Survey of India, Kolkata, 268 pp.) as well as Pinus (Pinaceae) and presumably polyphagous (Smith et al. 2020bSmith et al. 2020b:
Smith SM, Beaver RA, and Cognato AI. 2020b. A monograph of the Xyleborini (Coleoptera, Curculionidae, Scolytinae) of the Indochinese Peninsula (except Malaysia) and China. ZooKeys 983: 1-442. https://doi.org/10.3897/zookeys.983.52630)

Remarks

This species is strikingly similar to, and has been recovered as sister to Xy. saxesenii using COI data (Cognato et al. 2020bCognato et al. 2020b:
Cognato AI, Sari G, Smith SM, Beaver RA, Li Y, Hulcr J, Jordal BH, Kajimura H, Lin C-S, Pham TH, Singh S, Sittichaya W. 2020b. The essential role of taxonomic expertise in the creation of DNA databases for the identification and delimitation of Southeast Asian ambrosia beetles species (Coleoptera: Curculionidae: Scolytinae: Xyleborini). Frontiers in Ecology and Evolution 8: 27. https://doi.org/10.3389/fevo.2020.00027) but the elytralelytral:
pertaining to the elytra
morphology is inconsistent within single specimens. Given its close relationship with X. saxesenii the species is expected to have denticlesdenticle:
a small tooth, the sides of which are equal and the tip is above the middle of the base
along declivitaldeclivital:
pertaining to the elytral declivity
interstriae 1 and 3. However this is not always the case and the species can also have declivitaldeclivital:
pertaining to the elytral declivity
interstriae 1 and 2 unarmed with denticlesdenticle:
a small tooth, the sides of which are equal and the tip is above the middle of the base
along interstriaeinterstria:
longitudinal spaces along the elytra between the striae, which is not as<br /> impressed and bear smaller punctures.
3. Both tubercletubercle:
a small knob-like or rounded protuberance of the exoskeleton
patterns have been found on each elytronelytron:
the two sclerotized forewings of beetles that protect and cover the flight wings
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