Arasada pyraliformis Moore

Arasada pyraliformis Moore, [1885] 1887, Lepid. Ceylon 3: 189.

Arasada albicosta Hampson sensu Holloway, 1976: 15.

Diagnosis

The wings are typical of the genus, greyish buff, speckled and dotted darker, with irregular and, on the forewing, oblique dull ochreous fasciation. The forewing costa is narrowly paler, and the hindwing has a narrow, somewhat broken, straight medial fascia though this can be indistinct. The next species, albicosta, is smaller and when fresh, much darker, greyer; it has more neatly crenulate pale fasciae, with a clearer greyish area between the postmedial and submarginal of the forewing. The discal spot of the forewing tends to be more evident, rounded and clearly ringed with black in albicosta. The white fascia of the hindwing is usually straighter and more regular in albicosta, compared with Sundanian material of pyraliformis (this does not necessarily hold elsewhere). The genitalia of both sexes provide clear differences between the two species. Males of pyraliformis have genitalia that are more elongate, with the costal process of the valve expanded and flexed outwards, sometimes almost foot-shaped; in albicosta this process is straight and tapering. The saccular process in albicosta is narrower, digitate rather than scoop-like. In females, albicosta has a pair of sinuous structures within, and extending the length of, the lamella postvaginalis of the eighth segment, whereas pyraliformis has a pair of small, posteriorly directed lobes in a central postion. In both species the corpus bursae has a belt of small spines centrally as illustrated, these varying in size and number in both species.

Taxonomic note

Two further Arasada species may occur in Peninsular Malaysia, though one, represented by a single male, may be a hybrid between albicosta and pyraliformis. The facies of this latter is intermediate, and the genitalia (slide 20783) have the costal process tapering but flexed out, and the saccular process is small as in albicosta but apically hooked as in pyraliformis. The other, represented by an individual of each sex, has facies more as in pyraliformis, but the hindwing fascia is more continuous and gently curved, the concavity distad. The male genitalia (slide 20907) have the valve costal process short, not much more than the saccular one, and much shorter than the cucullus (the processes are longer than the cucullus in albicosta and pyraliformis). The saccular process is broad as in pyraliformis. The female (slide 21222) has the ostium within a massive pocket enclosed by the seventh segment, and the corpus bursae is long, narrow and finely scobinate, lacking a central belt of spines. Finally, A. javanica Hampson is endemic to Java. It is generally more ochreous than pyraliformis, and lacks white in the hindwing fascia.

Geographical range

Sri Lanka, India, Taiwan, Peninsular Malaysia, Sumatra (HS / ZSM), Borneo, Java.

Habitat preference

Single specimens have been taken from diverse habitats: from a boat in an area of mangrove in the Bay of Brunei; in disturbed coastal forest near Seria in Brunei; in a Paraserianthes falcataria plantation near Brumas in the lowlands of Sabah; from a cultivated area at 1050m at Kundasan on the slopes of G. Kinabalu; an older specimen from Bidi in the lowlands of Sarawak.

Biology

Moore (1884-1887: pl, 172) illustrated the larva of pyraliformis from Sri Lanka. The species was reared by Dr H. Steiner in Peninsular Malaysia during a survey of insects attacking rattan palms (Steiner, 2001). The mature larva (Plate 10) is a long, slender semi-looper with prolegs only fully developed on A5 and A6, with plantae extremely broad, three times the proleg width, giving the impression of an inverted ‘T’. The prolegs on A4 are minute, those on A3 absent. The head is distinctly broader than the body, dorsally rounded. The ground colour of the head and body is a pale greenish buff, marked with reddish brown in a slender reticulate pattern on each side of the head and in a series of broken and irregular longitudinal lines down the body on each side of a dorsal yellow stripe. This stripe is variable in thickness but generally narrow and extends as two lines onto the head; where the stripe is broadened, it is usually centred by lenses and streaks of reddish brown. The brown markings at the anterior of A2 and A3 are darker and more extensive dorsolaterally, with a transverse bar of ground colour immediately behind them, and a pale yellowish spot near the centre of each adjacent to the bar. When the larva is in a strongly looped posture, these patches appear as eye-like markings at the crest of the loop. Primary setae only are present but are as long as the thickness of the larva, and longer over the dorsal part of the gently sloping anal section.

The host plant recorded was Calamus (Palmae), the larvae being found on species of this genus in rubber plantations.