05 December 2009

Life History of the Common Awl

Life History of the Common Awl (Hasora badra badra)



Butterfly Biodata:
Genus: Hasora Moore, 1881
Species: badra Moore, 1858
Subspecies: badra Moore, 1858
Wingspan of Adult Butterfly: 47mm
Caterpillar Host Plants: Derris trifoliata (Leguminosae, Papilionoideae),
D. elliptica and two others (suspected to be Derris species).



A female Common Awl on the leaf surface of the Coconut Palm.

Physical Description of Adult Butterfly:
Adults are rather large in size with pointed forewing apex and markedly lobate hindwings. Above, the wings are dark brown. In the male, the wings are typically unmarked or with faint subapical spots. In contrast, the female has three pale yellowish subapical spots, large pale yellow hyaline spots in the cells and in spaces 2 and 3 on the forewing Wings bases of the female are ochreous. Below, both sexes are brown and often washed with purple, more so in pristine specimens. The forewing is pale yellowish to whitish at dorsum entering middle of space 2. On the hindwing, there is a small white roundish spot in the cell and an elongated white spot in the subtornal area. The spots on the forewing upperside correspond to those on the underside.


A female Common Awl with partially opened wings, showing us the various spots on its forewings

Field Observations of Butterfly Behaviour:
Adults are rarely seen in Singapore, likely due to its crepuscular nature. In contrast, the larval stages are rather readily found on various Derris species at multiple locations in Singapore. The adults are usually sighted in the vicinity of its larval food plants, typically ovipositing females. The usual perching site is on the underside of a leaf or other plant parts, resulting in photographs of "upside-down" adults being the most common takes of this species.


A male Common Awl on the underside of a leaf.


A male Common Awl pertching on the underside of a leaf.

Early Stages:

The 1st local host plant, Derris trifoliata, is a scandent shrub with 3-5 leaflets in a pinna, pink flowers, thin and flat pods. This plant is commonly found on coastal areas such as the Sungei Buloh Wetland Reserve and Kranji Nature Reserve.


Host plants : Derris trifoliata.

The 2nd host plant, Derris elliptica, is also a scandent shrub but with 9-15 obovate-oblong leaflets in a pinna and has brown pubescent branches. Extracts from both Derris species have been used as insecticides and by locals as "poison" for catching fish/shrimps.


Host plant : Derris elliptica.

Two other host plants, found in the nature reserves and in the Southern Ridges, are also woody climbers with 5-foliate and 7-foliate leaves. It is likely that they are Derris species too. The variegated early stages of the Common Awl feed on the young and still tender leaves of the host plants. The newly hatched and the 1st and 2nd instars typically feed on the youngest and still yellow/brown leaflets. Common Awl caterpillars of all instars also construct leaf shelters by joining leaf blades with silk threads.


Local host plants : unknown sp. #1 (left); unknown sp. #2 (right).


A mother Common Awl ovipositing on young shoots of Derris elliptica.

The eggs are laid singly on young shoots of the host plants. Each egg is white with a biege tinge. It is shaped like a pressed bun with a large flattened base (diameter: 0.9mm) and prominent ridges running from the pole to the base. The micropylar sits atop at the pole.


Two views of an egg of the Common Awl.


Mature egg (left), empty egg shell (right)

It takes 2-3 days for the collected egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 2mm. It has the typical cylindrical shape for skipper caterpillars, and the pale yellowish brown body has a number of moderately long setae. The large head is black, slightly bi-lobed and lightly hairy.


1st instar caterpillars. Top: early in this stage, length: 1.9mm.
Bottom: later in this stage, length :2.5mm.


The young caterpillar constructs its first leaf shelter by bringing two halves of a small young leaf together with silk threads. It rests within the flap and ventures out to eat on nearby leaf surface. In later instars, the Common Awl caterpillars also construct leaf shelters in a similar fashion but do so with larger and older leaves.


Leaf shelters and eggs found on young shoots and leaflets of unknown host #1.

After 2 days in 1st instar and reaching a length of about 4mm, the caterpillar moults to the next instar. The 2nd instar caterpillar has four faint yellowish dorsal bands, and a large number of faint yellowish rings on the body segments. Black dorso-lateral patches are found on the 3rd thoracic segment, 2nd, 4th, 6th and 8th abdominal segments.These patches increase in size as the caterpillar grows in this instar. All three thoracic segments are much smaller (narrower) compared to the abdominal segments, with the prothoracic segment being dark brown to black. The body and the head capsule are also covered in short fine setae.


2nd instar caterpillars. Top: early in this stage, length: 4mm.
Bottom: late in this stage,length: 8.5mm.


The 2nd instar caterpillar reaches a length of about 9mm, and after 2 days in this stage, it moults again. The 3rd instar caterpillar resembles the 2nd instar caterpillar but with more striking yellow coloration on the segmental rings and dorsal bands. This instar lasts another 2 days with the length reaching 14-15mm.


3rd instar caterpillars. Top: early in this stage, length: 9mm.
Bottom: late in this stage,length: 13.5mm.


The 4th instar caterpillar resembles the 3rd instar caterpillar closely. One noticeable change is the appearance of a pair of narrow black dorso-lateral patches on the 2nd thoracic segment. This stage takes about 6-9 days to complete with the body length reaching 25-29mm.


4th instar caterpillars. Top: early in this stage, length: 14mm.
Bottom: late in this stage, length: 25mm.


The final and 5th instar caterpillar has similar body markings and coloration as the 4th instar caterpillar. One unmistaken change is in the head capsule which has now become dark cherry red with three medium-sized black spots. The prothoracic segment is colored as per the head capsule and has a pair of black dorso-lateral stripes. Dense white setae cover the whole body. This stage takes about 6-9 days to complete with body length reaching about 41mm.


5th (final) instar caterpillars of the Common Awl. Lengths: 33mm (top); 36mm (bottom).


A close-up view of the head capsule of the final instar larva of the Common Awl.

Towards the end of 5th instar, the body of the caterpillar gradually shrinks in length. It ceases feeding and stations itself in its leaf shelter and enters the preparatory pupa phase. During the early part of this stage, the caterpillar spins large quantity of silk threads to seal the pupation shelter, and in particular, constructs a silk girdle at its 2nd/3rd abdominal segment and a short transverse silk band near its posterior end. Both the dorsal point of the girdle and the transverse band are also secured by vertical/oblique threads to the inner wall of the shelter.


Two views of a pre-pupa of the Common Awl.

After about 1 day of the pre-pupal phase, pupation takes place within the pupation shelter. The pupa secures itself with its cremaster attached to the transverse band. The pupa has a short thorax, a rather long abdomen and a black and pointed rostrum. Fresh after the pupation event, the body is pale yellow with large and cherry red spots (corresponding to the black patches on the larval body), but these fade 0.5 to 1 day later, and the body surface becomes mostly covered in a white substance. Length of pupae: 24-26mm.


Two views of a newly formed pupa. Note the red spots which will fade away within a day.


Two views of a pupa of the Common Awl with a coating of whitish powdery substance.


Sequence of three shots of the silk girdle from the pre-pupal to the pupal stage.
Note the girdle is suspended vertically with another silk thread to the shelter wall (or ceiling).


Three views of the posterior end from the pre-pupal to the pupal stage.
Note the transverse silk band and cremastral attachment to it during the pupal stage.



Two views of the cremastral attachment to the bundle of transverse silk strands.
Note the cluster of brown to dark brown hooks protruding from the cremaster to engage the silk threads.


After 6-7 days, the pupa becomes darkened in color signaling the imminent emergence of the adult. The next day the adult butterfly emerges from the mature pupa.


Two views of a mature pupa of the Common Awl



A newly eclosed Common Awl drying its wings near its pupal case.


A newly eclosed female Common Awl.

References:

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
  • Butterflies of Thailand, Pisuth Ek-Amnuay, 1st Edition, 2006
  • The Butterflies of Hong Kong, M. Bascombe, G. Johnston, F. Bascombe, Princeton University Pres 1999

Text by Horace Tan, Photos by Khew SK and Horace Tan.

4 comments:

Bluebottle said...

Another beautiful butterfly I have yet to see.

Horace said...

It is only a matter of time you come face to face with one during your future outings.
Try visiting Sungei Buloh Wetland Reserve where encounters are more likely.

Siyang said...

Is this Derris elliptica photographed in Singapore? This is because our local flora checklist only lists 3 Derris species, and Derris elliptica was not recorded in there.

Thanks!

Horace said...

Yes, it was photographed in Singapore in the Upper Seletar area. Either Khew and me could bring you to have a closer look at that plant.

It would also be good for you to take a look at another two suspected Derris plant which we are clueless about the ID.