Chen Ng(Pg61-69)

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

The S. graminum species group

The group is mainly accepted here following Cumming &

Cooper (1992). Members of this group are characterised by

an entirely black thorax and tomentose scutum, complete rows

of acrostichal setulae, lack of gland-like structures on male

abdomen (except S. spinicercus), at least 1 spine on the left

cercus of the male terminalia, and shortened female

terminalia. Two species found now from the Oriental region

belong to the S. graminum group. The group is most diverse

in the Palaearctic region (about 9 species), though at least 2

species of this group are known from the Nearctic and

Afrotropical regions.

Stilpon monospinatus, new species

(Figs. 1-4)

Material examined. – Holotype - male, THAILAND: Phang-Nga

province, Khao Sok, river banks in rain forest, sample n

°

 96035, 6

Apr.1996, coll. P. Grootaert (coll. RBINS).

Paratypes – 1 male, Phang-Nga, Khao Lak, Nangtong, beach

forest, sample n

°

 96046, 7 Apr.1996, coll. P. Grootaert (coll.

RBINS).

Diagnosis. – Species with black thorax. Male: mid femur with

3-4 yellow ventral bristles in basal 1/3, abdominal gland-like

structures lacking, left surstylus without surstylar comb, left

cercus with 1 short apical spine.

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

minute ocellars and moderately long inner verticals. Antenna

brownish yellow. Postpedicel nearly 2.0 times longer than

wide. Style about 5 times longer than postpedicel. Palpus pale.

Thorax black to dark brown. Scutum entirely tomentose.

Postpronotal bristle long, inclinate. Dorsocentrals in multiple

rows, complete posteriorly. Acrostichals 2-serial, complete

posteriorly.

Legs yellow with colour pattern: fore tibia and fore tarsomere

1 entirely brownish yellow, hind femur brownish yellow in

apical 1/2, mid femur with brownish tinge in apical part. Mid

coxa with 2 brown bristles on outer side. Hind trochanter

lacking spinules. Mid femur (Fig. 1) slender, with 3-4 yellow

long bristles in basal 1/3. Hind femur (viewed laterally) more

or less evenly thickened, with row of short (shorter than femur

is wide) anterodorsal bristles and row of prominent short

dorsal bristles. Fore tibia with 1 dark erect bristle in apical

part. Mid tibia with pale ventral spinules. Hind tibia

unmodified.

Wing normally developed, covered with uniform

microtrichia; with pattern consisting of 2 brownish, large,

Figs. 1-4. Stilpon monospinatus, new species, male. 1, mid leg, anterior view, 2, hypopygium, ventral view, 3, left surstylus, lateral view,

4, right surstylus, dorsal view; ap spn – apical spine, cerc – cerci, l lb – lower lobe of left surstylus, lft epand lam – left epandrial lamella,

m lb – medial lobe of left surstylus, rt epand lam – right epandrial lamella, rt sur – right surstylus, sur cm – surstylar comb, u lb – upper

lobe of left surstylus. Scale bar: 0.1 mm.

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THE RAFFLES BULLETIN OF ZOOLOGY 2004

elongate oval spots separated more or less distinctly by pale

basal half of vein M; remainder parts finely infuscate. Costal

vein with short setulae along anterior margin. Vein R2+3

about 2.5 times longer than Rs. Distance between apices of

R2+3 and R4+5 1.5 times longer than distance between apices

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

arcuate in apical part. Halter with elongate, contrastingly black

knob and pale stem.

Abdomen largely dirty yellow, lacking gland-like structures,

bearing mostly scattered dark setulae which are longer on

pregenital segments, with all tergites (except segment 8)

subequal in length, tergites 1-2 unmodified.

Hypopygium (Fig. 2) brown. Hypandrium with 4 long bristles

in apical part. Epandrium completely divided. Left epandrial

lamella small, fused to hypandrium, with 1 short bristle in

apical part. Left surstylus (Fig. 3) with upper lobe divided;

lower part rather small, subrectangular, with surstylar comb

greatly reduced, upper part elongate, slender, with short apical

spine. Right surstylus (Fig. 4) large, with excision on upper

margin, bearing numerous marginal bristles, lacking spines.

Left cercus unbranched, narrow, elongate, somewhat

broadened in apical part, with 1 short spine at apex, lacking

long bristles in basal part. Right cercus unbranched, nearly

as long as but almost 2 times broader than left cercus in middle

part, more or less rounded at apex, lacking spines, with some

short bristles on right margin. Phallus short.

Female. Unknown.

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

1.1 mm.

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

spine on the male left cercus.

Phylogenetic relationships. – The relationships of S.

monospinatus are unclear beyond inclusion within the S.

graminum species group, primarily due to the presence of an

apical spine on the male left cercus.

Distribution and seasonal occurrence. – Thailand. Known

from two localities of Phang-Nga Province. All records are

from April. Collected on river banks in rain forest and in beach

forest.

Stilpon spinicercus, new species

(Figs. 5-10)

Material examined. – Holotype - male, THAILAND: Chantaburi

Figs. 5-10. Stilpon spinicercus, new species, male. 5, mid leg, anterior view, 6, wing, dorsal view, 7, hypopygium, ventral view, 8, upper

lobe of left surstylus, dorsal view, 9, left cercus, right lateral view, 10, right surstylus, dorsal view; sur cm – surstylar comb. Scale bar: 0.1

mm.

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