26th Feb 2008

For the first time in many decades a butterfly species new to Sri Lanka has been identified in the Kurunegala district. A male Catopsilia scylla was observed and studied 2 Km from Wariyapola along the road to Kurunegala on the 18^th of February, 2008. The race to which this species belongs is yet to be determined.   

In flight, the butterfly looked very similar to Catopsilia pomona, but it was chrome-yellow below, and showed white and yellow scales above. Despite its name, there is no "Orange" in this population, at least so far. Its flight was also very similar to that of C. pomona, but its wing beats seemed less powerful, and it often flew low to the ground. Later that day, several more males were seen flying around a few tall shrubs of Cassia surattensis, an ornamental shrub planted along roadsides under the road beautification program in Sri Lanka. The location was visited the next day, and by 10 am several females arrived at the C. surattensis plants and began ovipositing. The females deposited their eggs very rapidly, mostly on the underside of mature leaves, though a few were laid on the upper side of the leaves as well. Females preferred a more vertical position to oviposit. The white eggs were very small and spindle shaped, and appeared to have a more slender stalks than those of C. pomona.

To get an idea of how far its range extended from Wariyapola, we drove north-west towards Puttalam (about 15 Km), east towards Anuradhapura (about 25 Km), and south-east all the way to Kurunegala. C. scylla was seen throughout the area traversed, but mostly in the vicinity of Cassia surattensis plants.  Although C. scylla is known to oviposit on Cassia fistula and Cassia tora in other countries, only a few of these plants were encountered on our journey. Although some of them carried eggs, no adults of C. scylla were seen near the plants. 

I suspect that C. scylla is as widely distributed in the island and as is C. surattensis, but this needs confirmation. Its flight period and the number of broods in a year are yet to be determined. It is likely that it will be similar to C. pomona with peak populations coincident with the onset of the monsoonal rains. However, given its predisposition to laying eggs on older leaves and the ability of the larva to feed on them, C. scylla may have different flight period/s and population peaks, specially if adult resources are not limiting after emergence. During the period under observation (18th Feb - 26th Feb), C. scylla was by far the more abundant species.  

C. scylla has a wide distribution in Asia and is found in southern Myanmar, the Malay Peninsula, Thailand, Vietnam, Java, Sumatra and Australia but has not been recorded from India or Sri Lanka in the past. It is rather puzzling that a common butterfly with enormous potential to multiply very rapidly and sustain large populations could have gone undetected for so long, unless it is a recent arrival and has established itself due to optimal conditions here. The assumption may be valid, particularly in Sri Lanka where collecting butterflies was a common hobby among the English and Europeans for at least 75 years, and a species such as this could not possibly have gone undetected under such intense collecting pressure. When it appeared on our shores is not certain. It may have been here since the first introduction of C. surattensis, but if this were so, it has gone undetected for a long time; C. surattensis  has been recorded in Sri Lanka for at least 17 years (see Flora of Ceylon, Vol. VII, pp81-82). Small populations may have survived on a few of these exotic plants and perhaps on our local C. fistula as well. But when the government started mass scale planting of C. surattensis along newly renovated roads, the butterfly populations may have multiplied very rapidly. On the other hand,  it may have arrived as eggs, larvae or pupa on some plant material  during a second wave of importation of plants from Thailand or Singapore, and passed through quarantine undetected; a possible theory, but  needs confirmation. But why import plants of C. surattensis at great expense when seeds would suffice?  - the plant produces a great many viable seeds and are easy to propagate. It is highly unlikely for C. scylla to have flown across the sea because of the large distances involved, unless it came from India across the Palk Straits, in which case, it would be a short distance though still formidable for a butterfly - the assumption would be that India is already colonized. However, to date, C. scylla has not been reported from India. Another possibility is that adults came across on ships, though this may be difficult to prove! 

Description: “♂♀. 60-65mm. Fore wing elongate; costa regularly and widely arched; apex moderately acute; outer margin short, slightly concave; tornus obtuse; inner margin long, about four fifths the length of costa; cell less than half the length of wing; vein 11 from cell well basad; vein 10 from near end of cell; 7+8 and 9 on a long stalk; 6 from the stem of 7+8, and 9 at about a third from end to apex; 5 from the cell, with mdc oblique and at least half as long as ldc. Hind wing very broad; costa strongly arched; apex not well marked; outer margin very slightly arched; tornus angular, well marked; inner margin almost straight from the base, slightly concave near apex; cell short and broad; mdc and ldc slightly oblique, the latter attenuate in its upper half; precostal vein short, curved slightly basad; vein 8 strongly angular near base. Antenna short and stout, not half length of fore wing; club long and gradual, truncate at apex. Palpus with third segment short and oval. Male with secondary sexual characters. Forewing underside near base of inner margin with a long hair pencil directed forwards; hind wing upper side, in area 7 near the base, with an oval patch of androconia.

♂ Upperside of forewing white; costa edged with black; outer margin with a narrow black border, wider at the apex, its inner edge dentate, from apex to tornus, and of nearly even width throughout. Hind wing rich cadmium-yellow, slightly paler towards the base, usually with small black marginal spots towards the veins.

♂ Underside rich cadmium or chrome-yellow. Fore wing with posterior area below the cell and vein 2 pure white; the yellow however, extends down to the tornal angle in a curve. Both wings with a discocellular spot, pinkish and ringed with darker brownish-pink; similar spots on the hind wings usually in the base of cell and in area 7 and 5, and below the origin of vein 2; usually a post-discal series of lunular diffuse markings of similar brownish-pink scales.

Antenna and upper side of head reddish-brown; thorax clothed with fuscous-grey hairs, abdomen yellow; underside of palpi, thorax and abdomen yellow.

♀ resembles the ♂. Upperside of forewing dull creamy white with a marginal black border; a post-discal series of ill-defined diffuse black spots curved strongly inwards anteriorly; often a small discocellular black ring. Hind wing as in the ♂, of a duller shade of yellow that turns to pale pinkish-white towards the basal area above the cell; a post-discal series, somewhat obsolescent, of dull brownish-black lunular markings; marginal spots much larger and duller in colour than in the ♂.

Underside as in the ♂, but all black markings on upper side replaced by rich pinkish-red tints.” 

From Talbot,G., The Fauna of British India including Ceylone and Burma, Butterflies Vol 1, 1947.

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