Redescription. Male (Figs 2–6): length: 11.5–14.2 mm, humeral width: 3.5–4.5
mm. Female (Fig. 1): length: 14.0–16.2 mm, humeral width: 4.5–5.4 mm. Body
black, in part provided with white to pale yellow pubescent maculae. Head with
white to pale yellow maculae on genae, borders of eyes, temple and two parallel
stripes between upper eye lobes; antennae black, with thin, whitish pubescence on
inner sides of first three segments and base of fourth segment, and scattered with
short, black bristles on undersides of first seven segments. Prothorax with a medial
white to pale yellow stripe, and each side white to pale yellow (Fig. 1a). Scutellum
white to pale yellow. Elytra with suture narrowly white to pale yellow near base; each
disc with 5 white to pale yellow maculae: a large oval spot close to suture at the end
of basal 1/4; a smallest spot near the middle, far from suture; the third one large,
oval, close to suture just behind the middle; the fourth medium in size, round, far
from suture; an oblique transverse band just before apex. Ventral surface covered
with dense white to pale yellow pubescence, thinly so along middle. Legs black,
thinly pubescent. Pronotum and elytral bases with sparse, erect, black bristles.
Head hardly broader than prothorax, deeply, and in part densely punctured, feebly
concave at vertex. Eyes deeply emarginate, inferior eye lobes subequal to (female),
or 2 times as high as (male) genae below it, width much less than half of front. Antennae
longer than body; scape slightly thickened apical without cicatrix nor a ridge;
antennomere ratio (male): 12 : 3 : 21 : 16 : 16 : 15 : 14 : 13 : 13 : 12 : 13; (female): 15
: 4 : 24 : 17 : 17 : 16 : 15 : 14 : 14 : 13 : 13. Prothorax almost as broad as long (male)
or broader than long (female), swollen laterally before middle; disc convex and somewhat
deeply and closely punctured. Elytra prominently angulate at humeri, slightly
narrowed apically; each with 2 humeral longitudinal ridges beginning after humeri
and reaching near the apex, truncated apically, with short and small teeth at the
suture and the outer angle, surface with coarse and irregular punctures. Legs stout,
middle tibiae grooved, hind femur reaching fourth abdominal segment, first hind tarsal
segment longer than (male), or nearly as long as (female) following two segments
combined. Male claws: the anterior claws of the fore and mid tarsi are toothed at the
base, but the tooth in the fore tarsus is very small (Fig. 5), the tooth in the mid tarsus
is long (Fig. 6, almost same size of the normal claw). Female claws simple.
Male genitalia (Figs 7–11): Tegmen length about 3.0 mm; lateral lobes stout,
each about 0.6 mm long and 0.3 mm wide, with fine haired ridge at the base (in
ventral view), apex nearly truncated and with fine setae which are shorter than lateral
lobes; ringed part elbowed in the widest portion, converging; basal piece bifurcated
distally (Fig. 9); median lobe plus median struts moderately curved, a little
longer than tegmen (6:5); the median struts about one half of the whole length of
median lobe; dorsal plate shorter than ventral plate; apex of ventral plate narrowly
pointed, with sharp apex which is always curved to right side (in ventral view, Fig.
10); median foramen elongated triangular, with a small projection in lateral view;
internal sac about 3 times as long as median lobe plus median struts, with 4 pieces
of basal armature, 2 bands of supporting armature and 3 rods; the two longer rods
each about 1.6 mm, shorter than tegmen, the short middle rod about 1.1 mm long.
Ejaculatory duct single. Tergite VIII (Fig. 8c) broader than long, apex truncated with
middle slightly projected, setae near lateral corner dense and long, and sparse and
short around middle.
Diagnosis. Differs from G. lacteomaculata Schwarzer, 1925 (Fig. 24), G. lacteomaculata
quadriguttata Pic, 1926 (Figs 25–26) and G. tonkinea Aurivillius, 1925 (Figs
30–33) in elytron having only one big oval macula at basal fourth, instead of two
small spots, the second macula smallest instead of the first one. Differs from G. laodice
Thomson, 1879 (Fig. 27) and G. subalcyone Breuning, 1964 (Figs 28–29) in elytron
without long and sharp tooth at the outer angle, having only one big oval macula at
basal fourth, instead of two spots.
Remarks. Based on the study on the types and material from type localities, we
agreed with Breuning (1956) that G. humerosa Gressitt, 1940 is conspecific with G.
coomani Pic, 1926. Though the holotype of G. humerosa Gressitt (Fig. 2) has the middle
oval pubescent spot reaching suture and seems to be different from the type of G.
coomani Pic (Fig. 1), the male (Fig. 4) also from Hainan Island looks no different from
those from Tonkin. Nevertheless, such pubescent markings are quite variable in shape
and size within same species.