In general, the adult members of this order are characterised by a head, thorax, abdomen, two antennae, two compound eyes and six legs, as well as four scale covered wings (two forewings, two hind wings) and a proboscis.

The wings of a butterfly vary enormously so the venation (or vein structure) on the wings can often be used to assist identification and classification.

Few butterflies emit any sound so organs for hearing are redundant and do not exist in butterflies but are present in some moths.

The highly sensitive antennae perform several functions; as detectors of food, as receptors for the scent of pheromones produced by the opposite sex and as means of avoiding objects. Its sense of taste, too is highly developed whereas its eyesight is generally poor, although they do see colour. For example, some species have been shown to be attracted to a particular colour: the Australian Blue Mountain Swallowtail (Papilio ulysses) the male is attracted to bright blue; mistaking it for a female.

The larva differs completely from the adult having a soft body, well developed head, and mandible mouth parts, and usually eight pairs of legs.

Classification

Class             INSECTA
Order             LEPIDOPTERA
Sub-order     DITRYSIA

Superfamily               HESPERIOIDEA (Skippers & Darters)
    Family                                Hesperiidae

Superfamily               PAPILIONOIDEA (Butterflies)
    Families                            Papilionidae
                                                Nymphalidae
                                                Lycaenidae
                                                Pieridae

All other Superfamilies Known as moths

The families of Acraeidae, Amathusiidae, Danaidae, Libytheidae and Satyridae have very recently been reclassified into the family of Nymphalidae.  The family of Riodinidae (one species in Sri Lanka; the Plum Judy) has now been incorporated into Lycaenidae.

The difference between butterflies, skippers/darters and moths is much debated amongst Lepidopterists and there are many exceptions to the list below. It could be said that butterflies are simply a group of moths that specialize in daytime flying.

However, ‘true’ butterflies are generally regarded as belonging to the superfamily Papilionoidea, skippers to the superfamily Hesperioidea and moths to the other twenty superfamilies of Lepidoptera.

Hesperioidea are often grouped with butterflies (they are mainly diurnal or active during the daytime). One visible difference between a skipper and a butterfly is that a skipper has hooks or points at the end of antennal knobs. Different species of skippers are very difficult to identify and it may require dissection to do so.

1. Moths usually rest with their wings in the horizontal ‘open’ position, butterflies rest with their wings closed vertically over their back.
2. In general moths are active at night whereas butterflies are active during the day.
3. Butterflies have slender clubbed antennae whereas moths have short, thick or feathery antennae.
4. Butterflies have slender, smoother bodies whereas moths’ bodies are often stout and furry or hairy-looking.
5. Most moths have a frenulum and nearly all butterflies lack one. A frenulum is one or more short spines projecting anteriorly from each hind wing of a moth, at the wing’s base. The frenulum acts like a hook, attaching to a small structure on the under-surface of the forewing. This ‘velcro’ pair of structures acts to hold both wings together producing a more coordinated flight.

Other differences occur at different times of the life cycle, for example at the pupa stage in a moth the larva is encased in a cocoon of silk whereas the butterfly larva is often exposed.

There are four stages in a butterfly’s life cycle:

• Ovum – Egg
• Larva – Caterpillar
• Pupa – Chrysalis
• Imago – Winged Adult

Ovum/Egg Stage
The butterfly lays its eggs (normally singly but sometimes in clusters) on the host plant (the host plant being the required food source of the larva). These eggs can be extremely diverse between species in colour and form; and as few people see the full cycle from egg, to pupa to emergent butterfly; little is known about the egg and pupa stage and knowledge is limited as to the identity of which species the resultant butterfly will be.

Larva/Caterpillar Stage
The larva of the butterfly is known as a caterpillar. The larva hatches from the egg (consuming the egg shell as it’s first meal), then continues to consume the host plant, moulting several times This shedding process is known as ecdysis and occurs a number of times, most commonly five times; and each period of growth between a moult is known as an instar. Each instar has differences in colours and markings, thus making identification of a species at the pupa stage yet more complicated. During the final instar or growth period the larva attaches itself it a suitable spot on which to pupate and then undertakes its final moult, revealing the pupa.

Pupa/Chrysalis Stage
As with the adult butterfly, there is great variation amongst the pupae of different species of butterfly, in form and adaptation; some are expertly camouflaged, for example The Cruiser (Vindula erota asela) hangs like a dead leaf, others are beautifully coloured with metallic hues, whilst others may hide in the darkness under tree bark. The pupa stage of different species again varies and can last weeks or even months.

Imago/ Adult Stage

Inside this pupa, the butterfly is undergoing extreme physical changes called a metamorphosis and will eventually emerge transformed into the adult winged butterfly or imago. Indication that the butterfly is about emerge comes when the pupa becomes translucent.

When the butterfly emerges, its wings are damp and it must rest upside down whilst they dry and the liquid from its swollen body is pumped into the veins in the wings. This may take minutes or several hours; during which time they are extremely vulnerable to predators.

The adult butterfly’s life span can range from one day to one year depending on species; however, more commonly it is of a few weeks duration.

The role of the food plants is extremely important in the life cycle of a butterfly.

In general, each species has its own species of food plant. Whilst the larva eats leaves and plant matter sometimes much to the annoyance of gardeners but more than recompensed by the beauty of the butterfly; the imago has a mainly liquid diet such as nectar from flowers, tree sap, moisture from the soil or rotting matter, enriched with minerals. Hence the larva has mandibles for chewing whereas the mouthpart of the adult is a proboscis, like a fine tube which allows their fluid diet to be sucked up.

It should not be forgotten, that by feeding on nectar and flying from plant to plant, the adult butterfly also performs the important task of pollinating flowers

Butterflies are most active in the morning between 9am and noon. Earlier than than that and they are often resting absorbing heat from the sun to increase their metabolic rate; after noon, when the day is hottest they often seek cooler areas.

Copulation in butterflies can last several hours and if the mating pair is disturbed, it is the female who will fly them to safety

Some are strong fliers and gallop such as the Papilios, others seem to have a faltering flight, some glide or sail, others seem to skip. Some fly at height barely resting, making them very difficult to observe, others are more ponderous in flight and seem to rest frequently such as the Danaids.

As with other characteristics of butterflies, they are very diverse and ingenious in their methods to avoid predation or attract a mate.

Mimicry

Some may use mimicry to appear like another animal; perhaps a bird as in the case of the Peacock Pansy (Junonia almanac). This species found in Sri Lanka has two very prominent eye spots, giving it the appearance of a much larger animal. This may well deter potential predators or the eyespots may encourage the predator to attack this area rather than the more life-threatening head area of the butterfly. The eyespots, however, may simply be a method of communication between a species or an evolutionary anomaly.

Some species of larva and butterfly are poisonous. For instance, the Common Jezebel (Delias eucharis) feeds on a plant which is toxic. It accumulates this toxicity and if eaten by a predator such as a bird, they will cause it to vomit. The predator will then avoid this species in the future. The Painted Sawtooth (Prioneris sita) mimics the wing markings of the Common Jezebel, thus also avoiding potential predators who may mistake it for the toxic Common Jezebel.

Toxicity
Another example of a species in Sri Lanka which uses toxicity to defend itself is the Indian Crow (Euploea core asela) which feeds on the poisonous plant Narium oleander.

Often these toxic species are brightly coloured with striking markings in both the larva and adult to alert would-be predators to the dangers of eating them.

Camouflage
Some butterfly species are so well camouflaged that they are impossible to detect even at close quarters. The Blue Oak Leaf (Kallima philarchus philarchus) is endemic to Sri Lanka and although it is brightly marked on the upper side of its wings, when the wings are closed in the resting position it looks exactly like a withered leaf.

Sexual Dimorphism
Many butterflies have brightly coloured wing markings to attract the opposite sex. Indeed many species show examples of sexual dimorphism. This is when the male and female differ greatly in their markings. Some examples of species that illustrate this trait in Sri Lanka are The Common Birdwing (Troides darsius); The Danaid Eggfly (Hypolimnas misippus) and The Tawny Rajah (Charaxes psaphon).

Seasonal Variation
Some species also have seasonal colours i.e. they differ in their dry season form and the wet season form such as the Spotless Grass Yellow (Eurema laeta) and The Lime Blue (Chilades lajus lajus).

Migration is a trait seen in many animals most commonly birds but also in butterflies and is usually seasonal.

Many species of butterfly are migratory and may swarm in huge numbers and some even make journeys of hundreds of miles. Researchers are only now starting to understand what the reasons for this may be and how the butterfly navigates on these journeys. It was previously thought that the butterfly used light sensitive molecules in its brain to calculate their direction of flight by combining the position of the sun with an inbuilt biological clock. Yet they still managed to fly even on cloudy days with little sunlight. They have now found, however, that the light sensitive molecules are also sensitive to magnetic fields, rather like an inbuilt compass.

In Sri Lanka there are about sixty nine species; mainly from the Pieridae family including The Great Orange Tip (Hebomoia glaucippe); The Lemon Emigrant (Catopsilia Pomona); and The Common Albatross (Appias albina daranda) amongst others which migrate towards the Hill Country and Adam’s peak from January to May.

In Sri Lanka, the myth is that these swarms of butterflies are pilgrims on their way to Adams Peak.

For its size, Sri Lanka is one of the most biologically diverse countries on the planet. It has a monsoonal climate and can be divided into five climatic zones:

1. Low Country Wet Zone which covers the southwest of the island
2. Central Hill Zone encompassing the Hill country in the centre of the island
3. Intermediate Zone which is the transitional area between the central hills and the plains
4. Low Country Dry Zone covers the north, east and south east part of the island and is the largest zone in the island
5. Arid Zone which is the tip of the northwest of the island and the tip of the south east part of the island

There are 243 species of butterfly in Sri Lanka (including skippers/darters); 20 of which are endemic.

Their geographical distribution on the island is influenced primarily by climate, altitude and season as these are the factors affecting the food plant availability of each species.

There are two seasons in Sri Lanka. Normally from about May to September the south-west monsoon brings rain to the south-west and to the hills facing the wind (the wet zone) leaving the rest of the country fairly dry. During the other months the north-east monsoon blows bringing rain to the north and less so, to the east and south-east (dry zone), also to the hills and the southwest, with most rain falling between November and February.

There are two major butterfly cycles on the island when the numbers peak at the start of the monsoons. However some species are present in numbers all year round, irrespective of seasonal influence

Like many species in the world, butterflies in Sri Lanka are under pressure from human development leading to deforestation and destruction of the butterfly’s habitat; converting natural forest to agricultural land or human habitation. The existence of a species of butterfly is inextricably linked to its feeding plant. As most species of butterfly has a single species of plant food, if this plant food is destroyed then it will have an inevitable effect on the survival of the butterfly, perhaps even leading to extinction.

In many Sri Lankan myth and legend there are tales of migrations of vast numbers of butterflies to Adam’s peak but now these numbers seem to have diminished so we are undoubtedly already seeing man’s effect on this island.

According to the IUCN (the International Union for the Conservation of Nature) Red List website, the status of one Sri lankan speices, The Sri Lankan Rose (Atrophaneura jophon) was listed as critically endangered and two others, The Ceylon Tree Nymph (Idea iasonia) and the Ceylon Tiger (Parantica taprobana) were listed with the status of lower risk/near threatened. However, this information is based on data last gathered in 1996 so may not be a true reflection of the current situation. In fact, more recent local reports seem to indicate for example that the Ceylon Tiger has been sighted in reasonable numbers in the Hill country. However, this does not mean that the outlook is a positive one; indeed, it is more likely that many more species may be facing imminent threats to their continued survival.

It is vital that each one of us plays our role in ensuring the conservation of the butterfly in Sri Lanka; and it can be easily achieved by planting host plants for the larva and nectaring plants for the adult. The rewards will be immense as the fascinating world of the butterfly unfolds in your garden.

Butterflies in profusion tell us that all is well with nature. When they are in decline it is an indication that other wildlife may be heading the same way. It is not simply just a question of saving one species of butterfly, or even one family but about preserving and safe-guarding the delicate balance upon which the future of the entire ecosystem of this beautiful and richly bio-diverse island hangs.

• An illustrated guide to the Butterflies of Sri Lanka by Rajika Gamage
• Butterflies of Sri Lanka by Arittha Wikramanayake and Ariesha Wikramanayake
• A Selection of the Butterflies of Sri Lanka by John and Judy Banks
• http://www.lepsoc.org
• http://en.wikipedia.org/wiki/Lepidoptera
• http://www.iucnredlist.org
• http://www.telegraph.co.uk/earth/wildlife/7855868/Monarch-butterflies-use-internal-compass-to-find-their-way.html
• http://tolweb.org
• http://en.wikipedia.org
• http://bugguide.net