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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.