Chen Ng(Pg61-69)

323

THE RAFFLES BULLETIN OF ZOOLOGY 2004

mid tarsomeres 5 brownish (in darker specimens also mid

femur somewhat brownish in apex); otherwise legs yellow.

Hind trochanter with 2 brown spinules. Mid femur (Fig. 15)

slender, with 1 long anterior subapical bristle and row of 4

yellow, rather long, ventral bristles. Hind femur (viewed

laterally) evenly thickened toward middle, with 1 row of

anteroventral bristles becoming longer toward apex of femur

(3 subapical bristles longest) and some hardly prominent

dorsal bristles in basal part. Fore tibia lacking prominent

bristles. Mid tibia straight, slender, with hardly prominent

ventral spinules. Hind tibia slightly arcuate, with ventral

setulae more distinctly prominent.

Wing normally developed, covered with uniform

microtrichia; almost uniformly infuscate, somewhat deeper

along longitudinal veins. Costal vein with ordinary short

setulae on anterior margin. Vein R2+3 about 2 times longer

than Rs. Distance between apices of R2+3 and R4+5 nearly

2 times longer than distance between apices of R1 and R2+3.

R4+5 and M almost parallel and slightly arcuate in apical

part. Halter with contrast black elongate knob and pale yellow

stem.

Abdomen yellowish, lacking gland-like structures, with

segments 1-2 unmodified, bearing mostly scattered short

setulae, segment 8 with moderately long bristles.

Hypopygium (Fig. 16) dark brown, rather small. Hypandrium

with 2 long bristles just beyond its middle. Epandrium

completely divided. Left epandrial lamella small, fused to

hypandrium, lacking bristles in apical part. Left surstylus (Fig.

17, 18) with upper lobe divided; lower part lacking surstylar

comb, upper part large, subglobular, with 1 short bristle. Right

surstylus (Fig. 19) large, hemispherical. Left cercus

unbranched, digitiform, lacking spines, with 2 long and 1

shorter bristles in apical part. Right cercus undivided, short,

subrectangular, lacking spines, with several short bristles.

Phallus short.

Female. In most respects identical to male. Palpus brownish

yellow. Hind trochanter lacking black spines. Terminalia

shortened. Segment 8 normally sclerotized. Proximal margin

of sternite 8 without 2 anteriorly directed rods. Apex of

sternite 8 hinged and partially separated from base. Sternite

10 uniformly sclerotized, not fused with ventroapical margin

of tergite 8. Cercus elongate oval, brownish yellow, clothed

in setulae of different length.

Measurements. – Body length 1.4-1.7 mm, wing length 0.9-

1.2 mm.

Etymology. – The name refers to the Isaan region where the

species was found.

Phylogenetic relationships. – The relationships of this species

are unresolved beyond inclusion within the S.  seeluang

species group.

Distribution and seasonal occurrence. – Thailand. Known

from one locality in the Loei province. Quite common with

records from the end of April to the beginning of August,

October and December. Collected in bamboo wood and also

from riverbanks in gallery forest.

Stilpon laawae, new species

(Figs. 20-24)

Material examined. – Holotype - male, THAILAND: Nakhon

Nayok, Chulachomkla, along brook in shade, sample n

°

 97163, 12

Nov.1997, coll. P. Grootaert (coll. RBINS).

Paratypes – 1 male, same locality as holotype. Loei province,

Na Haeo FIRS in Malaise trap, 3-10 Sep.1999, coll. P.

Grootaert; 1 female, coll. Verapong Kiatsoonthorn & P.

Grootaert; 1 male, Na Haeo, Chang Tok waterfall, sample n

°

23035, 17 May.2003, coll. P. Grootaert (in coll. SWU &

RBINS).

Diagnosis. – Species with yellow thorax, most similar to S.

isaanensis differing from it in having quite long acrostichal

and dorsocentral bristles throughout, hardly prominent

postpronotal bristle and very short left cercus male terminalia.

Description. – Male. Head black in ground-colour, with

minute ocellars and inner verticals. Postpedicel pale yellow,

paler than scape and pedicel, nearly 2.0 times longer than

wide. Style about 5 times longer than postpedicel. Palpus

yellow.

Thorax almost wholly yellow. Scutum entirely tomentose,

scutal spots almost invisible, postpronotal calli dark.

Postpronotal bristle hardly prominent. Dorsocentrals in

multiple rows. Acrostichals 2-serial.

Legs yellow, with colour pattern: fore tibia (except base) and

fore tarsomere 1 brown; otherwise legs yellow. Hind

trochanter lacking spinules. Mid femur (Fig. 20) slender, with

4 long yellowish bristles in basal part. Hind femur (viewed

laterally) evenly thickened toward middle, with 1 row of

anteroventral bristles becoming longer toward apex of femur

(3 subapical bristles longest) and some hardly prominent

dorsal bristles in basal part. Fore tibia greatly incrassate,

lacking prominent ventral bristles. Mid tibia lacking

prominent ventral spinules. Hind tibia unmodified.

Wing (Fig. 21) normally developed, covered with uniform

microtrichia, finely infuscate. Costal vein with ordinary short

setulae on anterior margin. Distance between apices of veins

R2+3 and R4+5 about 2.0 times longer than distance between

apices of veins R1 and R2+3. R4+5 and M slightly divergent

and evenly arcuate in apical part. Halter with contrast black,

elongate knob and pale yellow stem.

Abdomen largely brownish yellow, lacking gland-like

structures, with segments 1-2 unmodified, bearing mostly

scattered short setulae; tergites 1-2 yellowish, segment 8 with

2 very long and several shorter bristles.

Hypopygium (Fig. 22) pale brown, small. Hypandrium with

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