Stictodex dimidiatus

Taxonomic history

Xyleborus dimidiatus Eggers, 1927a: 404.

Stictodex dimidiatus (Eggers): Hulcr and Cognato, 2013: 125.

Synonyms

Xyleborus dorsosulcatus Beeson, 1930: 219. Smith et al. 2020b: 310.

Xyleborus tunggali Schedl, 1936d: 32. Hulcr and Cognato, 2013: 125.

Xyleborus decumans Schedl, 1953b: 301. Hulcr and Cognato, 2013: 125.

Xyleborus cruciatus Schedl, 1973: 90. Hulcr and Cognato, 2013: 125.

Xyleborus spicatus Browne, 1986: 95. Smith et al. 2022b: 166.

Diagnosis

2.4−3.3 mm long (mean = 2.96 mm; n = 5); 2.54−2.89 times as long as wide. Stictodex dimidiatus can be readily distinguished by the antennalantennal:
pertaining to the antennae
club very broad, type 2 (obliquely truncatetruncate:
appearing cut off or suddenly shortened
), with segment 1 straight; elytralelytral:
pertaining to the elytra
declivitydeclivity:
downward slope of either the pronotum or elytra
with first and second interstriaeinterstria:
longitudinal spaces along the elytra between the striae, which is not as<br /> impressed and bear smaller punctures.
divergent, broadest at elytralelytral:
pertaining to the elytra
summit; declivitydeclivity:
downward slope of either the pronotum or elytra
flat and gradually sloped; scutellumscutellum:
a shield-like sclerotized plate located at the midpoint of the elytral base 
flat, flush with elytra; pronotumpronotum:
the dorsal surface of the thorax
tight around head; protibiaeprotibia:
tibia of the first pair of legs
inflatedinflated:
blown up; distended
on posteriorposterior:
toward the rear end; opposite of anterior
face.

Specimens of this species demonstrate an extreme morphological continuum of variation in the elytralelytral:
pertaining to the elytra
striae (both on discdisc:
the flat central upper surface of any body part (e.g. pronotum and elytra)
and declivitydeclivity:
downward slope of either the pronotum or elytra
) with it ranging from slightly to deeply impressedimpressed:
a depression in a surface
.

May be confused with

Arixyleborus species which share a broad antennalantennal:
pertaining to the antennae
club but possesses distinctive elytralelytral:
pertaining to the elytra
ridges and furrows.

Distribution

China (Yunnan), Indonesia (Maluku), Laos, East and West Malaysia, Myanmar, New Guinea, Sri Lanka, Thailand, Vietnam

Host plants

Most host records are from the Dipterocarpaceae, but other tree families are also occasionally attacked (Browne 1961b as Xyleborus decumans and X. tunggali).

Remarks

This species is remarkably morphologically variable. Further study using molecular data will be required to assess species limits.

DNA data

Sequences available for COI and CAD:

COI: HM064122; MN620003

CAD: HM064300; HM064301