definition of this subfamily has been given in the previous section: reduction or atrophy of tympanal organs; reduction of hindwing veins
through loss of M1, M2, one anal vein and sometimes one branch of CuA;
wasp-like appearance. This last is manifested in the reduced hindwings,
black forewings with white, yellow or transparent spots or patches, and a
black abdomen that is often ringed with yellow or white; the antennae may
sometimes have a subapical or apical white zone.
The male and female genitalia offer no clearly diagnostic features, though
sternite 8 in the male is usually considerably reduced in length relative
to the tergite. In the female the dorsal glands associated with the
ovipositor lobes are usually extensive, branched and slender. In the bursa
copulatrix a pair of signa is considered plesiomorphic, seen also in
Lithosiinae and many Arctiinae.
In Amata Fabricius and Trichaetoides Gen. n. is a
pair of signa. M2 and M3 are often stalked in the forewing, and M3 and
CuA1 connate or stalked in the hindwing (Figs. 2, 4). These features are
seen also in Streptophlebia Hampson, where the forewing is
otherwise strikingly modified: There are two pale spots or windows in the
forewing space posterior to CuA2 in most Amata and some Trichaetoides;
in the next group of genera there is ever only one.
Caeneressa Obraztsov, Eressa Walker, Syntomoides Hampson
and Auriculoceryx Gen. n. have a single signum in the bursa.
Caeneressa and Eressa have the three hindwing veins well
separated; in the other two genera they are reduced to two.
Hampson (1898) and Seitz (1912-1913) assigned numbers of Sundanian taxa to
genera such as Ceryx Wallengren and Trichaeta Swinhoe. No
Bornean species examined appears to be related to the type species of
Many Syntominae are day-flying; others fly by night and can be taken at
light. It is possible that, as with day-flying Arctiinae (p. 63 ff.),
darkness of abdominal sclerotisation is correlated with the day-flying
The larvae have rings of verrucae with brushes of setae on each segment;
the setae are not as long as in typical Arctiinae. Host-plant records are
not numerous, but they embrace a variety of plant families and include
(Bell, MS) mosses and lichens.
The genus Atucia Watson, proposed as a replacement name for Acutia
Kaye (in Watson, Fletcher & Nye (1980)) contains the single Bornean species
bidensis Kaye. This taxon proves to be a zygaenid closely related to Thyrassia
penangae Moore (Peninsular Malaysia) and therefore Atucia must
sink to Thyrassia Butler syn. n., and the Bornean taxon becomes Thyrassia
bidensis Kaye, comb. n.
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