Chen Ng(Pg61-69)

321

THE RAFFLES BULLETIN OF ZOOLOGY 2004

Paratypes – Pethburi province, Pa Dang, 1 male, 25 Mar.2001

(coll. RBINS).

Diagnosis. – Species with yellow thorax. Can be readily

distinguished from all other species of this group by vein

R2+3 flattened at apex.

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

minute ocellars and short 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, postalar calli dark. Postpronotal

bristle hardly prominent. Dorsocentrals in multiple rows,

complete posteriorly. Acrostichals 2-serial, complete

posteriorly.

Legs with colour pattern: hind femur brownish yellow in

apical 2/3; otherwise legs yellow. Hind trochanter lacking

spinules. Mid femur (Fig. 11) 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. Mid

tibia straight, slender, lacking prominent ventral spinules.

Hind tibia slightly arcuate, with more distinctly prominent

ventral setulae and unmodified posterior apical comb.

Wing normally developed, covered with uniform microtrichia,

finely infuscate, somewhat deeper along longitudinal veins.

Costal vein with ordinary short setulae on anterior margin.

Vein R2+3 flattened at apex, about 1.5 times longer than Rs.

Distance between apices of R2+3 and R4+5 nearly 3.0 times

longer than distance between apices of R1 and R2+3. R4+5

and M 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. 12) brown, small. Hypandrium with 2 long

bristles in apical part. Epandrium completely divided. Left

epandrial lamella small, fused to hypandrium, with 1 minute

bristle in apical part. Left surstylus with upper lobe (Fig. 13)

divided; lower part small, slender, lacking surstylar comb,

upper part moderately large, subglobular, lacking bristles.

Right surstylus (Fig. 14) large, elongate, covered with spinules

in apical part. Cerci almost completely fused into one lobe,

lacking spines, with several bristles of different length in basal

part; left cercus hardly prominent, short, rectangular; right

cercus pointed at apex. Phallus short.

Female. Unknown.

Measurements. – Body length 1.5-1.7 mm, wing length 1.1-

1.3 mm.

Figs. 11-14. Stilpon crassinervis, new species, male. 11, mid leg, anterior view, 12, hypopygium, ventral view, 13, upper lobe of left surstylus,

dorsal view, 14, right surstylus, dorsal view. Scale bar: 0.1 mm.

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322

Shamshev & Grootaert: A review of the genus Stilpon from the Oriental region

Etymology. – The name of this species refers to the widening

of the tip of vein R4+5.

Phylogenetic relationships. – The relationships of S.

crassinervis are unresolved beyond inclusion within the S.

seeluang species group. However, the presence of 2 very long

bristles on the segment 8 of the male abdomen, the general

structure of the male terminalia and, especially, the greatly

reduced cerci suggest this species is allied with S. laawae, S.

nhamyaaw, and S. taksin.

Distribution and seasonal occurrence. – Thailand. Known

from two provinces rather south: Phang-Nga and Petchaburi.

Records from the end of March to the beginning of April.

Stilpon isaanensis, new species

(Figs. 15-19)

Material examined. – Holotype - male, THAILAND: Loei

province, Na Haeo, riverbanks in gallery forest at FIRS, sample n

°

2017, 23 May.2000, coll. P. Grootaert (SWU).

Paratypes – Na Haeo, malaise trap at FIRS: 1 male, 22-

29.Oct.1999; 1 male, 42, 7-18.Dec.1999; 1 male, 12-28

Jun.2000; 1 female, 29.Apr-6 May.2001; 1 male, 12/61, 29-

5.Aug.2001, coll. Verapong Kiatsoonthorn & P. Grootaert

(in coll. SWU, RBINS, ZRC). 1 male, 4 females, Khring Nam

Tok, sample n

°

 23041, 20 May.2003, coll. P. Grootaert; 1

male, 1 female, Malaise trap in bamboo wood at FIRS, 24

May.2003 (leg. P. Grootaert). (in coll. SWU, RBINS and

ZRC).

Diagnosis. – Species with yellow thorax. Fore tibia and

tarsomere 1 brownish, postpronotal bristle long, scutal pattern

indistinct, rows of acrostichal and dorsocentral bristles very

short posteriorly.

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

inconspicuous ocellars and moderately long inner verticals.

Antenna with pedicel yellow, postpedicel brown. Postpedicel

nearly 2.0 times longer than wide. Style about 5 times longer

than postpedicel. Palpus pale yellow.

Thorax almost wholly yellow. Scutum entirely tomentose,

with 2 pale brownish, indistinct, posterolateral spots,

including postalar calli which are deeper darkened; scutellum

and postnotum with brownish posterior margin; pleural

sutures (especially in darker specimens) brownish in varying

extent. Postpronotal bristle long, brown, inclinate.

Dorsocentral and acrostichal setulae very short on prescutellar

depression.

Legs yellow with colour pattern: hind femur in apical 2/3,

fore tibia (except extreme base), fore tarsomere 1, fore and

Figs. 15-19. Stilpon isaanensis, new species, male. 15, mid leg, anterior view, 16, hypopygium, ventral view, 17, left surstylus, lateral view,

18, upper lobe of left surstylus, dorsal view, 19, right surstylus, dorsal view; u lb – upper lobe of left surstylus. Scale bar: 0.1 mm.

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