Early stage of Detached Dart (Potanthus trachala)

Butterfly description:
The species is moderately common in Singapore and not rare in Peninsula Malaysia, it can be found at all usual elevations, in both primary and secondary forest. Range from India to China and Sundaland. The adult have been observed to visit flowers and sunbathing.

Further reading: Identification of Potanthus trachala

Host plant description:
Imperata cylindrica, Lalang (Singapore)
Ischaemum barbatum (HK)
Neyraudia reynaudiana (HK)
Panicum maximum (HK)


Early stage description:
The eggs of Potanthus trachala are laid singly on the underside of the grass blade of the host plant. The dome-shaped egg is creamy white.The early stage of the Potanthus trachala complete in 6th instar.

Egg of P. trachala (day 1).

Maturing egg of P. trachala with head capsule visible through the 

egg shell (day 3)

It takes 3 - 4 days for the egg to hatch. After emergence, the caterpillar will devour the rest of the egg shell. The newly emerged caterpillar is creamy white with black head capsule, and a black line right behind the capsule on the prothorax. There're also numerous long and tiny hair (setae) at the posterior end of the body.

Caterpillar of P. trachala hatching sequence (day 4).

The body color of the 1st instar larva turns to greenish after a few feeding sessions on the grass blade.  The instar lasts about 5 days.

1st instar larva of P. trachala

1st instar larva of P. trachala, moulting to 2nd instar

The 2nd instar larva and subsequent instar larva continue to have the clear black line on prothorax, the black line continue to presents on the subsequents instar, slightly faded on 6th instar but clearly visible. The anal plate of the 2nd instar larva is black. The instar lasts about 5 days.

2nd instar larva of P. trachala

The 3rd instar larva resembles the 2nd instar larva, with black head capsule, black line behind the head capsule, and black marking on the anal plate. The instar lasts about 4-7 days.

3rd instar larva of P. trachala

The 4th instar larva has yellowish-green coloration on body. The instar takes about 6 - 8 days to complete.

4th instar larva of P. trachala

Internal structure of the leaf shelter of 5th instar larva

In the 5th instar, the head capsule is dominated by large and broad yellowish white lateral patches. This instar takes about 5 - 7 days to complete.

2 views of the 5th instar larva of P. trachala

5th instar larva of P. trachala, moulting to 6th instar

The 6th instar larva resembles the 5th instar larva, with the black line on prothorax slightly faded but visible. This instar takes about 11-13 days to reach the stage of pre-pupa. The body length reached 30 mm.

2 views of the 6th instar larva of P. trachala

Head capsule view of 5th and 6th instar larva

Anal plate of 6th instar larva

Towards the end of the 6th instar, the body coloration of the caterpillar changes to yellowish brown and shortens. Pupation takes place in the tight leaf shelter.

2 views of the leaf shelter

Similar to other in the genus, pupa of Potanthus trachala is without cremaster attachment or any silk girdle to secure itself to. White substance are found within the leaf shelter. The pupa is mainly greenish yellow. Length of pupae : 16mm.

Partial view of pupa after opening the leaf shelter

Two views of the pupa

Front-view of the pupa

Tail-part of the pupa

2 days before eclosion, abdomen of pupa start to turn darker, together with the eyes and thorax areas.

3 views of semi pupa of Potanthus trachala (2 days before eclosion)

1 day before eclosion, the head and thorax of pupa become darken and semi transparent. Upper-side wings marking briefly visible.

2 views of mature pupa (1 day before eclosion)

A newly emerged female Potanthus trachala

Note: 3 eggs collected from the same female, hatched into 2 female and 1 male. Each larva mature at different speed and reached pupation stage 4 days apart. 1 female pupated on days 41, 1 male pupated on days 44, the last female pupated on days 45. From egg to adult took 51 - 53 days.

All larvae are kept in similar condition (room temperature and humidity).



REFERENCE:
* A Photographic Monograph on Hong Kong Butterflies (vol 4). HKLS.
* M. J. Bascombe, G. Johnston & F. S. Bascombe, 1999. The Butterflies of Hong Kong.
* Corbet, A. S. & H. M. Pendlebury, 1992. The Butterflies of the Malay Peninsula. 4th Edition (Revised by J. N. Eliot).