Butterfly Survival Strategies - Part 2

Butterfly Survival Strategies - Part 2
Cryptic colouration, masquerade, startle, dazzle and decoy

A Dark Blue Jungle Glory perches on a leaf. Its cryptic undersides will render the butterfly well camouflaged when it forages amongst dead leaf litter on the forest floor.

In the first part of this series, we saw how some butterfly species have evolved to mimic their unpalatable cousins for protection against predators. This phenomenon of protective colouration gives the mimic a better chance of survival in the field, and in particular, females of the species, a higher odds of survival long enough to lay her eggs for the next generation.

A typical forest floor covered with dead leaf litter and twigs. Can you spot the two butterflies feeding on rotting matter on the forest floor?

In this part, we look firstly at adaptive colouration of butterflies based on the need of concealment or crypsis (defined simply as a strategy to reduce the probability of detection). This principle of concealment throught colouration was discussed by AR Wallace as the "visual similarity between animal and its background". This theory has been explained by many examples in the animal world - from the white polar bears that live in essentially white snow-covered habitats, to the colour differences in marine animals like sharks where its dorsal and ventral colour differences help in concealment of its presence in its environment, depending on whether viewed from above or below.

Camouflage

Saturns feeding on rotting fruit. How many can you see in the picture?

There are many examples in butterfly evolution, where cryptic colouration has been employed to render the butterfly 'invisible' to predators. This is done via disruptive patterning and colours to resemble its surroundings. The objective here of course, is the theory supporting the notion that predators 'cannot attack what the cannot see'.

Another Dark Blue Jungle Glory well camouflaged amongst dead leaf litter on the forest floor

Cryptic colouration, coupled with the behaviour of the various butterfly species in their preferred habitats is one of their survival strategies to avoid being predated upon for as long as possible.

Five large Morphinae with cryptic colouration on the undersides of the wings. With eyespots, lines that break the silhouette and colours that blend in with the forest floor habitats that they frequent, their camouflage help them stay 'invisible' from predators as they feed. Clockwise from top left - Koh-I-Noor (Amathuxidia amathaon), Tufted Jungle King (Thauria aliris), Giant Saturn (Zeuxidia aurelius), Dark Jungle Glory (Thaumantis noureddin) and Palm King (Amathusia phidippus)

Flash and Dazzle

In what is described as "startling patterns", prominent eyespots in butterflies have been shown to divert the attention of inexperienced avian predators. In his experiments with the Peacock Butterfly (Inachis io), David Blest (1957) found that this 'startle display' made young birds back off, even if for a moment, giving the butterfly that fleeting moment to escape. Locally, related species like the Junonia probably have the same effect on predators.

Large eyespots on the wings of the butterflies that may startle would-be attackers into hesitating for a fleeting moment will allow the butterfly to escape with its life

Another example of this strategy is the Great Helen (Papilio iswara iswara). At rest with its wings opened flat, the butterfly's forewings conceal the white patch on the hindwings, making it appear totally black. But when started, it flashes the white patch to 'dazzle' a would-be predator momentarily, giving it a precious moment to make good its escape.

The Great Helen is a good example of a species that employs "dazzle" to startle its would-be attacker. When at rest, the large white patches of the wings are hidden. When alarmed, it takes off, flashing the white patches that may catch the attacker off-guard whilst it is startled for a moment

Many species of butterflies also display an array of eyespots - some on the uppersides and some on the undersides of the wings. Eyes or the display of eyes, tend to make a predator wonder if there are indeed any other animal lying in wait for it. A momentary hesitance makes a difference in whether the butterfly escapes or ends up as lunch.

Eyespots on the outer fringe of the wings of some Satyrinae may cause some inexperienced predators to hesitate as they check out the eyes.

In some species like the Mycalesis, the spots are always ranged along the outer margins of the wings, never close to the body. Even if a predator decides to attack the 'eyes', it will take out a part of the butterfly's wing that may not be critical, allowing the butterfly to escape with its life, albeit without a small piece of its wings.

Masquerade

The Leaf Butterfly is a pretty iridescent blue above with orange bands, but when alarmed it settles with its wings closed to resemble a dead leaf.

As an alternative to purely employing cryptic patterns to camouflage itself, some butterfly species employ the strategy of masquerading as a non-palatable part of its environment, or at least 'pretend' to be something else to conceal itself. The famous Leaf Butterfly (Kallima limborgii) in Malaysia and (Kallima inachus) in Thailand and northwards, and (Kallima paralekta) in Java and southwards, demonstrates this method of concealment.

Another shot of the Leaf Butterfly masquerading as a dead leaf whilst it feeds

On the upperside, the butterfly is a rich purple blue, with a broad orange subapical band on the forewing. The underside very closely resembles a dead leaf, complete with a midrib, petiole and even patches of fungal growth on the leaf!

The undersides of the Autumn Leaf and Saturn also resemble dead leaves. Note the colourful orange upperside of the Autumn Leaf when it spreads its wings to sunbathe.

In Singapore, several other species like the Autumn Leaf (Doleschallia bisaltide) and to a certain extent, the Saturn (Zeuxidia amethystus) are less successful examples of trying to masquerade as dead leaves.

Decoy

Many Lycaenids display "false heads" complete with eyes and antennae to fool predators into attacking the "wrong" side of the butterfly

Many Lycaenidae are excellent examples of employing the strategy of creating 'decoys' whereby a predator is fooled into attacking the less vital parts of the butterfly. These species have evolved to create a 'false head' whereby the tornal area of the hindwing featuring a prominent 'eye' with one or more pairs of tails making them appear like antennae. Indeed, in the field, many of these species also accentuate this part their hindwings by moving them up and down when at rest, causing the 'false head' to be more active and calling attention to the 'wrong side' of the butterfly to a would-be predator.

Underside of the Common Red Flash featuring false eyes and antennae. Below is a shot depicting a possible survivor of an avian attack with the hindwings showing bite marks in a previous encounter.

The filamentous white-tipped tails of many species are also very 'lively' when wafted in a breeze, as are the long and white tails of many of the long-tailed Lycaenids. Coupled with the patterns, colours and tails, these butterfly species create a 'decoy' false head so that a predator attacks a less vital part of the butterfly, giving it a chance to survive and escape, but without a piece of its hindwings.

An Ambon Onyx showing off its "false head"

So now we see, despite being virtually harmless and unable to defend themselves with any aggressive 'weaponry', natural selection has allowed butterflies to adapt and evolve other strategies to even the odds of survival in the field via the colours and shapes of their wings, and their behaviour in their preferred habitats.

Text by Khew SK : Photos by Goh LC, Khew SK, Tan CP & Yong San

Life History of the Colour Sergeant

Life History of the Colour Sergeant (Athyma nefte subrata)

Butterfly Biodata:
Genus: Athyma Westwood, 1850
Species: nefte Cramer, 1779
Subspecies: subrata Moore, 1858
Wingspan of Adult Butterfly: 60mm
Caterpillar Host Plants: Glochidion brunneum (Euphorbiaceae), G. superbum (Euphorbiaceae) and one un-identified plant in the nature reserve.


The upper- and underside of a female -f neftina Colour Sergeant.


The upper- and underside of a female -f subrata Colour Sergeant.


The upper- and underside of a male Colour Sergeant.

Physical Description of Adult Butterfly:
The adult has a closed cell in the forewing. The upperside of the forewing has contiguous/conjoined white cell post-discal spots from the dorsum to spaces 2 and 3. and confluent post-discal spots in spaces 4, 5 and 6 with their inner edge in line. The sexes are dissimilar. The male is a rich velvety black, with white markings tinged with bluish. The male in Singapore typically has an orange sub-apical spot in space 6 on the forewing upperside. This spot is usually white for males found in the Malay Peninsula. The female occurs in two distinct forms. In the -form neftina (Fruhstorfer) the wings are marked with broad orange-brown stripes arranged in the usual manner. The -form subrata (Moore) is a dark dull chocolate brown, with narrow and rather diffuse tawny brown markings. Both female forms are less abundant than the male, with -f neftina appears to be more common among the two female forms.

A female -f neftina Colour Sergeant.


A female -f subrata Colour Sergeant perching on a leaf in a western wasteland.

Field Observations of Butterfly Behaviour: This species is relatively common in Singapore. Sightings of the fast flying adults are rather frequent and widely distributed, both in nature reserves and urban parks. In sunny weather, both sexes can be found flying in the vicinity of flowering shrubs and taking nectar.


A female -f neftina Colour Sergeant visiting a ripened fruit of the Singapore Rhododendron.


Another female -f neftina Colour Sergeant perching on a leaf of the Singapore Rhododendron.

Early Stages:


Host plant: Glochidion brunneum.


Host plant: Glochidion superbum.


Host plan: an unidentified plant in the nature reserve with leaves playing host to a number of Colour Sergeant caterpillars.

Thus far, two species of Glochidion and one un-identified plant (likely to be a Glochidion sp. too) have been identified as the local host plants. Caterpillars of the Colour Sergeant adopt the same feeding and frass-management routines as described for the Commander and other Athyma species in earlier blog articles.

Two views of an egg of the Colour Sergeant.

The eggs of the Colour Sergeant are laid singly at the tip of a leaf on the host plant. The dark yellowish eggs are somewhat globular in shape, with its surface marked with hexagonal pits and bearing short spines at pit corners, giving them the appearance of minute sea-urchins. Each egg has a diameter of about 1mm.

Two views of a mature egg of the Colour Sergeant. The head and mandibles are visible in the right view.

The egg takes about 2-3 days to hatch. The young caterpillar emerges by eating away part of the egg shell. The rest of the egg shell becomes the first meal for the newly hatched, which has a cylindrical pale yellowish green body covered with many small tubercles and short setae. The head capsule is pale to dark brown in color.


A newly hatched caterpillar of the Colour Sergeant, length: 1.8mm.

Similar to the feeding habit of the other Athyma spp., the 1st instar caterpillar of the Colour Sergeant also feeds from the leaf tip and leaves the midrib intact and protruding. A frass chain is also constructed laboriously by the young caterpillar at the tip of the exposed midrib. Between feeds, the caterpillar rests on either the exposed midrib or the frass chain. In later instars, the caterpillar tends to rest near where the protruding midrib joins the remaining lamina. At this site, it also attempts to camouflage itself with a collection of frass pellets secured with silk threads to the lamina.


Two views of a 1st instar caterpillar of the Colour Sergeant. Length: 5mm.

One 1st instar caterpillar resting on the exposed midrib/frass-chain structure.

After reaching about 4.5-5.0mm in about 3 days, the caterpillar moults to the 2nd instar. The body color of the 2nd instar caterpillar is dark brown with a green undertone. There are a number of small and dark dorsal and lateral patches. Besides tiny tubercles covering most of its body surface, the 2nd instar caterpillar also features short and branched spines dorso-laterally and spiracularly. The head capsule is dark brown and dotted with a number of conical tubercles. This instar lasts about 2-3 days with the body length reaching 6.5-7.0mm.


Two views of a newly moulted 2nd instar caterpillar, length: 4.8mm


2nd instar caterpillar, late in this stage, length: 6.8mm

The 3rd instar caterpillar has slightly longer dorsolateral spines, with pairs on thoracic segments longer than the rest. Its head capsule is dark brown to black irorated with pale brown tubercles. Broad pale brown markings on abdominal segments 3 and 5 with a diamond-shape outline become increasing prominent during this stage. This instar takes about 3 days to complete with body length reaching about 10-11mm.


Two views of a 3rd instar caterpillar, length: 8.5mm


Two views of 3rd instar caterpillar, late in this stage. .Length: 11mm.

The 4th instar caterpillar has much longer dorso-lateral spines which are heavily branched. The body is brown to black in color. Besides conical tubercles, the head capsule also carries some short spines. Broad pale green markings appear on the dorsum of the 1st and 3rd abdominal segments. Also, pale brown to pinkish brown marking appears on the 5th abdominal segment. This instar lasts 3-4 days with body length reaching about 18mm-19mm.


Two views of a newly moulted 4th instar caterpillar, length: 11mm.


Two views of 4th instar caterpillar, late in this stage. Lengths: 14.5mm.

In the 5th (final) instar, the branched dorso-lateral spines very well developed on all body segments with those on the meso- and metathorax being the longest. Newly moulted caterpillar has yellowish brown body colour with broad dorsal markings on the 1st and 3rd abdominal segments and a broad black dorsal marking on the 5th abdominal segment. The body base color soon changes to a uniform green color as growth proceeds in this instar, leaving only the saddle marking on the 5th abdominal segment in contrasting reddish/pinkish brown. The dark brown head capsule has much longer and pointed spines.


Two views of 5th instar caterpillar, early in this stage. Lengths: 20.5mm.


Two views of a 5th instar caterpillar, later in this stage, length: 30mm.

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.
Two views of a 5th instar caterpillar adopting an on-guard stance.

The 5th instar lasts for 4-5 days, and the body length reaches up to 35mm. On the last day, the base body colour changes to yellowish green and then to yellow. Rather large dark markings, roughly circle in shape, also appear laterally.


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

Additional dark patches have appeared dorsally and laterally.

Two views of a 5th instar caterpillar, late in this stage, with base color changed to yellow.

Soon, the caterpillar ceases feeding and wanders around. Eventually it chooses a spot on the underside of branch/stem/leaf and spins a silk pad from which it hangs vertically to take on the pre-pupatory pose.

Pre-pupatory larva of the Colour Sergeant.

Pupation takes place a day later. The pupa suspends itself from the silk pad with no supporting silk girdle. It is almost entirely pale brown in color with segments and parts outlined in a darker shade of brown. A few gold patches also adorn the pupal surface. The abdominal segments are slender, and the thoracic portion being larger and expanded laterally. Dorsally, there are two prominent processes curved towards each other. When disturbed, the abdominal segments flex laterally, and could stay in that position for a period of time. Length of pupae: 23-25mm.

The pupation event of a Colour Sergeant caterpillar.

Three views of a pupa of the Colour Sergeant.


A pupa of the Colour Sergeant sighted on the underside of a leaf in the nature reserve.

After about 5-6 days of development, the pupal skin turns translucent as the development within the pupal case comes to an end. The spots and streak on the forewing upperside also become discernible. The next day, the adult butterfly emerges from the pupal case, typically during the morning hours.

Three views of a mature pupa of the Colour Sergeant.

The eclosion event of a male Colour Sergeant at 2x speed.

A newly eclosed Colour Sergeant resting on its pupal case.

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

Text by Horace Tan, Photos by Sunny Chir, Federick Ho,  Khew SK and Horace Tan.