Microperus nanus (Browne) Beaver & Hulcr, 2008

Beaver, Roger A. & Hulcr, Jiri, 2008, A Review of the Ambrosia Beetle Genus Cryptoxyleborus Schedl (Coleoptera: Curculionidae: Scolytinae), The Coleopterists Bulletin 62 (1), pp. 133-153 : 133-153

Microperus nanus (Browne) new combination

Cryptoxyleborus nanus Browne, 1949:903 .

Xyleborus caelator Browne, 1955: 354 (unnecessary replacement name for Xyleborus nanus Blandford 1896 )

Taxonomy: This minute species, only 1 mm long, and perhaps the smallest xyleborine known, was described from the female by Browne (1949) in the genus Cryptoxyleborus . Later (Browne, 1955), he described the male and transferred the species to the genus Xyleborus Eichhoff renaming it X.caelator to avoid homonymy with X.nanus Blandford (1896) . Browne (1961) included the species in the Xyleborus exiguus species group, which is now placed in the genus Xyleborinus Reitter. The holotype (BMNH) and series of specimens from Brunei and East Malaysia in MSU, RAB and ZMLU have been examined. The form of the pronotum, declivity obliquely attenuated instead of acutely pointed, antennal club type 1, and flat protibia with no granules on its posterior side clearly exclude the species from Cryptoxyleborus , whilst the antennae and submerged scutellum indicate that it should be placed in the genus Microperus Wood (see Hulcr et al. 2007 a) rather than Xyleborinus .

Distribution: East Malaysia ( Sarawak), West Malaysia. The species is newly recorded here from Brunei Darussalam and East Malaysia (Sabah).

New Records: BRUNEI: Temburong, nr. K.Belalong FSC, 4 ° 33 9 N, 115 ° 09 9 E, 150 m, ex Shorea sp. , 25.ii.1992 (R.A.Beaver) ( RAB) ; MALAYSIA, Sabah, Sipitang, Mendolong , 25.iv.1988, 3.v.1988 (S.Adebratt) ( ZMLU) ; Sabah, Danum Valley , 117 ° 48.75 9 E, 5 ° 01 9 N, ex Parashorea malaanonan under bark, 11.vii.2006 (J.Hulcr) ( MSU) .

Biology: This species is associated only with Dipterocarpaceae . It has previously been recorded from several species of Shorea and from Hopea ferrea ( Browne 1961; Beaver & Browne 1979). It is unusual among Xyleborina in breeding solely in the phloem layer, and not in the xylem. The gallery system is simple, the entrance leading to a gallery which usually follows the circumference of the stem at the xylem–phloem junction. It is enlarged in one or more places to form small chambers in which the eggs are laid and the larvae develop. Brood sizes are quite small (9–15, mean 5 10.8, n 5 6) ( Browne 1961; pers.obs. RAB). It will attack both large logs and small stems down to 1.5 cm diameter ( Browne 1961; pers.obs. RAB).