06 September 2008

Life History of the Lance Sergeant

Life History of the Lance Sergeant (Athyma pravara helma)

Butterfly Biodata:
Genus: Athyma Westwood, 1850
Species: pravara Moore, 1858
Subspecies: helma, Fruhstorfer, 1906
Wingspan of Adult Butterfly: 60mm
Caterpillar Host Plants: Uncaria spp. (Rubiaceae)

A female Lance Sergeant checking out a leaf for oviposition

A Lance Sergeant puddling among leaf debris on a forest trail

Physical Description of Adult Butterfly:
Above, the Lance Sergeant is dark brown to black with an interrupted, white, macular and curved fascia running from mid-costa on the forewing to near the base of the dorsum on the hindwing. There are submarginal lines of white markings irrorated with dark scales on both wings, that on the hindwing taking the form of a broad band running from the apex to dorsum. Lance Sergeant can be distinguished easily from other similar Athyma species in that the cell-streak in the forewing is entire and clavate at its distal end. The underside is greyish brown with markings as on the upperside.

Field Observations of Butterfly Behaviour:
Locally the Lance Sergeant is uncommon. Sightings of adults have been confined to a few locations in the northern and western part of the Central Catchment Nature Reserves where its host plants, Uncaria spp. are growing. The adults fly with a strong swift flight. Individuals have been seen puddling on trails and at stream banks during past sightings.

Early Stages:
Species of Uncaria are climbers with opposite leaves and short petioles. They climb with the aid of a pair of cat-like claws which are modified lateral branches at the base of the leaves. For this reason, the South American U. tomentosa is called Uña de Gato (Cat's Claw). Some Uncaria species are medicinal plants in various parts of the world. Notably, one species, U. gambier, played an important part in Singapore's early history (and economy) prior to the introduction of Rubber.

Host plant #1: Uncaria sp.

Host plant #2: another Uncaria sp.

The "claws" on an Uncaria plant.

A female Lance Sergeant ovipositing on a leaf of the host plant.
Left: abdominal tip just touches the leaf tip; Right: egg laid at leaf tip.

The eggs of the Lance Sergeant are laid singly at the tip of a leaf on the host plant. In a behavior typical of Athyma spp. (and some other species), the mother butterfly first lands on the surface of the leaf, and with its head pointing towards the petiole, it reverses until its abdomen tip reaches the drip tip of the leaf, and there it lays an ovum. Damaged leaf edges, caused by other insects or even the feeding activity of an early caterpillar, could be mistaken as the leaf tip, with the result of an egg being laid there. Diameter of egg: about 0.8mm.

Eggs of Lance Sergeant at laid at leaf tips of the host plant.
Left: freshly laid; Right: mature egg. Diameter: 0.8mm.

The egg takes 3 days to hatch. The young caterpillar eats its way out of the mature egg, and then proceeds to finish up the rest of the egg shell. The newly hatched has a cylindrical dark greenish brown body covered with many small tubercles. The head capsule is orange in base color and speckled with dark brown patches.

Newly hatched Lance Sergeant caterpillar, length: 2mm

The 1st instar caterpillar feeds from the leaf tip and works its way towards the base on each side of the midrib, which is left protruding. At the tip of this exposed midrib, the young caterpillar also laboriously builds a frass chain which is made up of frass pellets strung together with silk thread. Between feeds, the caterpillar rests on either the exposed midrib or the frass chain. If disturbed when feeding on the nearby leaf lamina, it also makes a hasty beeline for this resting position. In later instars, the caterpillar tends to rest near where the protruding midrib joins the remaining lamina. At this site, it also attempts to disguise itself with a collection of frass pellets secured with silk on the lamina. After reaching about 5mm in about 3 days, the caterpillar moults to the 2nd instar.

1st instar caterpillar resting on the frass chain, length: 5mm

Besides the tiny tubercles covering most of its body surface, the 2nd instar caterpillar also features bigger and more prominent branched spines dorso-laterally and spiracularly. Black spots also line the basal part of the dorso-lateral spines. The head capsule is now brown to dark brown in coloration.
This instar lasts 3 days with the body length reaching 7mm.

2nd instar caterpillar, early in this stage, length: 5mm

2nd instar caterpillar resting on its frass chain

Compared to the earlier instar, the 3rd instar caterpillar has longer dorsolateral spines, with the pairs on thoracic segments particularly longer. Its head capsule is dark brown to black irorated with pale brown tubercles of both rounded and pointed shapes. Sub-spiracular white patches can be found on abdominal segments 2, 6-8, enveloping the short branched spines found there. This instar takes 3-4 days to complete with body length reaching about 12mm. On the last day of this instar, the dorsal band takes on a greenish tinge.

3rd instar caterpillar, early in this stage, length: 8mm

3rd instar caterpillar, late in this stage, length: 12mm

3rd instar caterpillar, dormant before the moult to the next instar.
Note the bulge behind the head capsule, this will become the new head.

The 4th instar caterpillar has a wide dorsal band which is briefly yellowish green at first but soon turns bright green for most part of this instar. The sub-spiracular white patches are now more prominent, and the dorso-lateral spines have grown further in length and changed to crimson red in color. The head capsule has two faint vertical pale stripes running vertically. This instar lasts 4 days with body length reaching about 16mm.

4th instar caterpillar, early in this stage, length: 10.5mm

4th instar caterpillar, length: 13.5mm

The next moult brings the caterpillar to its 5th and final instar. Now there is a drastic change in appearance. The branched dorso-lateral spines are now very well developed on all body segments, those on the meso- and metathorax being the longest. Newly moulted caterpillar has a broad green dorsal band and is dark yellowish green laterally, but soon the green on the dorsal band spread laterally giving the caterpillar an overall green appearance. The two white vertical stripes on the head capsule also become much more prominent in this instar. As with other members of the Limenities subgroup, when disturbed, the caterpillar adopts a characteristic posture with the anterior body arched and the head tucked beneath the thorax.

5th instar caterpillar, early in this stage, length: 16mm

5th instar caterpillar of Lance Sergeant

The 5th instar lasts for 6-8 days, and the body length reaches up to 29-31mm. On the last day, its body color changes dramatically. The color changes first to yellowish green and then pale brown. The caterpillar ceases feeding and wanders around for a pupating site which could either be a branch or a leaf surface. Once a suitable spot is found, the caterpillar spins a silk pad, and from which it hangs vertically to take on the pre-pupatory pose.

5th instar caterpillar, last day in this instar

5th instar caterpillar, a few hours before the dormant pre-pupal stage.

A pre-pupatory larva of Lance Sergeant

Pupation takes place a day later. The pupa suspends itself from the silk pad with no supporting silk girdle. When disturbed, the abdominal segments flex laterally, and could stay in that position for a period of time. It is almost entirely silverly-gold in color with segments and parts outlined in brown. The pupa has a pair of curved and pointed cephalic horns. The abdominal segments are slender, and the thoracic portion being larger and expanded laterally. Dorsally, there are two prominent processes curved towards each other. Length of pupae: 17-19mm.

Two different views of a pupa of the Lance Sergeant.

A pupa of the Lance Sergant: fresh pupa (left), mature pupa (right).

After 7 days of development, the pupa turns black in the wing pad area as the development within the pupal case comes to an end. The spots and streak on the forewing upperside are also discernible. The following day, soon after day break, the adult butterfly emerges from the pupal case.

An eclosion sequence of a Lance Sergeant

A newly eclosed Lance Sergeant

Another newly eclosed Lance Sergeant, showing us the undersides.

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
  • The Butterflies of Hong Kong, M. Bascombe, G. Johnston, F. Bascombe, Princeton University Press 1999
Text and Photos by Horace Tan