Stictodex dimidiatus (Eggers, 1927)

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

Stictodex dimidiatus (Eggers, 1927) Fig. 74

Xyleborus dimidiatus Eggers, 1927a: 404.

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

Xyleborus dorsosulcatus Beeson, 1930: 219. syn. nov.

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

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

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

Type material.

Paratype Xyleborus dimidiatus (NMNH,1). Holotype Xyleborus dorsosulcatus (FRI). Lectotype Xyleborus tunggali (NHMW).

New records.

Laos: Kham Mouan, Ban Khun Ngeun, 18°07'N, 104°29'E, ~ 200 m, 24-29.iv.2001, Pacholátko (RABC, 1). Vientiane, Ban Van Eue, 15.xii.1965, native collector, ex malaise trap (BPBM, 3); as previous except 15.ii.1966 (BPBM, 1). Vietnam: Dong Nai, Cat Tien N.P., 11.40817, 107.38098, 134 m, 20-22.ii.2017, VN81, A.I. Cognato, T.A. Hoang, ex FIT (MSUC, 2). Quang Tri, Huong Hoa distr., Huong Hoa Nature Reserve, near Cup village, 16°56'15"N, 106°34'52"E, 400 m, 6.xi.2007, G. Csorba (HNHM, 1).

Diagnosis.

2.4-3.3 mm long (mean = 2.96 mm; n = 5); 2.54-2.89 × as long as wide. Stictodex dimidiatus can be readily distinguished by the antennal club very broad, and type 2, with segment 1 straight; declivity with first and second interstriae divergent, broadest at elytral summit; declivity flat and gradually sloped; scutellum flat, flush with elytra; pronotum tight around head; protibiae inflated on posterior face. Specimens of this species demonstrate an extreme morphological continuum of variation in the elytral striae (both on disc and declivity) ranging from slightly to deeply impressed.

Similar species.

Arixyleborus spp.

Distribution.

Indonesia (Maluku), Laos*, East & 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 as currently defined is remarkably morphologically variable (Fig. 74 ). Further study using molecular data will be required to assess species limits.

Images of a X. dorsosulcatus paratype were examined. The specimen represents the most extreme declivity seen in S. dimidiatus with striae 1 deeply impressed (Fig. 74C, D, F ). Because X. dorsosulcatus falls within the continuum of variation, it is here placed in synonymy with S. dimidiatus .

Figures

Figure 74. Dorsal, lateral and declivital view of Stictodex dimidiatus, 2.4 - 3.3 mm. Specimen exhibiting typical S. dimidiatus morphology (A, B, E), specimen exhibiting morphology of the synonym X. dorsosulcatus (C, D, F).