Life History of the Full Stop Swift

Life History of the Full Stop Swift (Caltoris cormasa )

Butterfly Biodata:
Genus: Caltoris Swinhoe, 1893
Species: cormasa Hewitson, 1876
Wingspan of Adult Butterfly: 32-34mm
Caterpillar Local Host Plants: Ottochloa nodosa (Poaceae), Panicum maximum (Poaceae, common name: Guinea Grass), Ischaemum ciliare (Poaceae, common name: Smut Grass).

Physical Description of Adult Butterfly:

On the upperside, the wings are dark brown with hyaline spots in spaces 2,3 and 4, subapical spots in spaces 6 and 7 and two cell spots in the forewing. The upper cell spot is typically either absent or small in comparison to other Caltoris spp. On the underside, the wings are ferruginous brown, usually with a purplish tinge.

A close-up view of the forewing upperside, showing two small cell spots of a Full Stop Swift.

The upperside view of a newly eclosed Full Stop Swift. The upper cell spot is absent  while the lower cell spot is small.

A Full Stop Swift visiting flower in a wasteland.

Field Observations of Butterfly Behaviour:

The Full Stop Swift is moderately common in Singapore. The adults have been sighted in multiple locations including forested areas, wastelands, urban parks and gardens across the island. The adults fly with a swift, strong and darting flight.

Early Stages:

The Full Stop Swift have been bred on a number of grass species, three of which have been identified: Ottochloa nodosa, Panicum maximum and Ischaemum ciliare. The caterpillars feed on leaves of the host plants, and live in shelters formed by joining edges of a grass blade together.

Local host plant #1:Ottochloa nodosa.

Local host plant #2:Panicum maximum.

The eggs are laid singly on the upperside of a grass blade of the host plant. Each dome-shaped egg is reddish with white fuzzy patches on the lower half. The micropylar sits atop and a number of very fine and obscure  ridges running longitudinally from it. The basal diameter is about 1.2-1.3mm.

Full Stop Swift caught in the act of ovipositing on two separate occasions.

Two views of an egg of the Full Stop Swift.

Maturing eggs on the 2nd last day (left) and the last day (right) of the oval phase.

It takes about 4.5-5 days for the egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 2.2mm. Its orangy body is cylindrical in shape and has a tuff of few moderately long setae at the posterior end. The head capsule is black. A black collar mark can be found the dorsum of the prothorax. The newly hatched nibbles away most of the egg shell remnant before proceeding to construct its first leaf shelter.

Two views of a newly hatched caterpillar, length: 2.2mm

A newly hatched caterpillar in its very first leaf shelter. Further "stitching" work by the caterpillar will bring the two opposite edges together.

The body turns yellowish green after the caterpillar has a few sessions of the leaf diet. By the time the caterpillar lies dormant for its moult to the 2nd instar, its length has reached 5.5mm. The 1st instar takes a total of 3 days to complete.

Two views of a 1st instar caterpillar, length:4mm.

The 2nd instar caterpillar still has a yellowish green body, and the head capsule is still black. The black collar mark on the prothorax has faded to just to hint of its presence. This instar lasts about 4 days with the body length reaching about 7.5-8.5mm.

Two views of a 2nd instar caterpillar, length: 5.5mm.

The 3nd instar caterpillar still has a black head capsule but its body is now much paler yellowish green compared to the 2nd instar. There is no longer any trace of the black collar mark on the prothorax. This instar lasts a total of 4-5 days with the body length reaching about 12-13mm.

Two views of a 3rd instar caterpillar, early in this stage, length: 9.2.

A 3rd instar caterpillar, late in this stage, length: 11mm.

The 4th instar caterpillar resembles the 3rd instar caterpillar closely. In some specimens, the head capsule is no longer entirely black as pale brownish lateral patches can be observed. This penultimate instar lasts 4-5 days with the body length reaching up to 20-23mm.

A 4th instar caterpillar with head capsule bearing brownish lateral patches. length: 17mm.

Two views of a 4th instar caterpillar, late in this stage, length: 20mm.

The 5th instar caterpillar has a pale yellowish body. In a drastic change, its head capsule is now whitish in ground colour but reddish brown along the periphery and various sulci (groove/furrow). Two reddish brown stripes rise from the adfrontal area, giving the appearance of a chinese character 山. The anal plate is unmarked as in the all previous instars. This final instar takes about 6-8 days to complete with the body length reaching 37-38mm.

Two views of a 5th instar caterpillar, top: 27mm, bottom: 34mm.

Two views of a 5th instar caterpillar, late in this stage, length: 35mm.

Towards the end of 5th instar, the body of the caterpillar shortens in length and body colour assumes a uniform shade of pale lime green. It seeks out the underside of a leaf blade and forms a shallow but half-open shelter with silk threads at both ends. The body excretes a moderate amount of white waxy material at this stage. Within the shelter, a silk girdle and a silk pad are then spun. Once the caterpillar attaches its claspers to the silk pad, it enters the dormant prepupatory phase which lasts about one day.

Two views of a dormant pre-pupa of The Full Stop Swift.

The pupa secures itself with the silk girdle and with its cremaster attached to the silk pad. It has a short thorax, a rather long abdomen, a short and pointed rostrum. The body is uniformly deep lime green with no markings. Length of pupae: 28-30mm.

Two views of a pupa of a male Full Stop Swift, length: 29mm.

After 7 days, the pupa becomes mostly black in color in the wing pads and in the body segments. Eclosion takes place the next day.

Two views of a mature pupa of the Full Stop Swift, shortly before the eclosion event.

A newly eclosed Full Stop Swift.

References:

• [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society, 1992.
• Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
• A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2010.

Text by Horace Tan, Photos by Benjamin Yam, Koh Cher Hern, Chng CK and Horace Tan