(This week, since I do not know too much about butterflies I have also picked on the knowledge of Dr. Michael van der Poorten, who is one of Sri Lanka’s leading butterfly experts)
NATURE has provided us with many beautiful things that we continue to admire each day – birds, flowers, butterflies, trees, shrubs etc. Of all those that we admire so much and marvel at their beauty, butterflies are what many of us know least about.
Sharman Apt Russel in her book An Obsession with Butterflies says, “There are some 18,000 species of known butterflies and 147,000 species of moths.
They are all classified scientifically as Lepidoptera”. Scientifically butterflies are catergorised as belonging to the super family Papilionidea, which is divided into five families. They are the families Papilionidae, Pieridae, Lycaenidae, Riodinidae and Nymphalidae.
The differences between butterflies and moths are that most butterflies fly during the day whilst most moths fly at night.
Most butterflies are brightly coloured whilst most moths are drab. Most butterflies have distinctly clubbed antennae whilst those of the moth are straight, plumed or filamentous. Butterflies generally rest with their wings closed above their bodies whilst the moths rest with their wings spread out.
Michael van der Poorten is one person in Sri Lanka who has been looking very closely at our butterflies. He is currently studying their ecology, habits, distribution, and flight periods in order that recommendations for conservation may be made.
Michael, a product of Trinity College in Kandy, obtained a BSc (Honours) degree in Agriculture from the Peradeniya University.
He obtained his Masters and PhD in Canada and returned to his property in Kurunegala after many years. Since his return he has continued his in-depth studies on our butterfly fauna.
Asked for a brief overview on our butterflies, Michael said, “There are 242 different species of butterflies recorded in Sri Lanka. However, not all of them are found everywhere, all year round, in the island.
Some are found only in the hills while others are found in the lowlands and yet others are found only on the driest areas of the island. Some are found only from September to December, others only in August”.
“The reason for such a distribution is the egg laying habits of the females and the availability of appropriate food plants for the larvae. Females of a given species lay their eggs on only certain types of plants.
For example the ‘Ceylon Tiger’ butterfly is found only above 4000′ feet elevation because the plant on which the female of this butterfly lays its eggs is found only in the upcountry hills and not elsewhere.
So the distribution of butterflies in Sri Lanka is closely related to the distribution of the plants on which the butterflies lay their eggs, with the exception of those butterflies that migrate long distances”.
“Most butterflies are seasonal and are seen primarily after the flush of fresh tender leaves on which the butterfly caterpillars feed. As the season advances the tender food material for the young caterpillars become limiting and their numbers decline”.
The young caterpillar emerges from the egg two to three days after the egg has been laid and immediately begins feeding. Although the great majority of butterfly caterpillars feed on leaves, some feed on developing pods or fruits or flowers.
The caterpillar of one species of butterfly in Sri Lanka avoids plants altogether and feeds only on live mealy bugs. Caterpillars often need to feed and grow rapidly before the food supply runs out or the plants on which they feed become less palatable due to maturation.
As the caterpillar grows, its skin becomes too tight and it is shed several times to accommodate the larger size. This is a process called molting.
Michael also said, “Caterpillars face many difficulties in their lives but the greatest threats are from birds, lizards and wasps that feed on them. Caterpillars have evolved many different mechanisms to avoid enemies.
Some caterpillars are remarkably well camouflaged and are indistinguishable from the leaves and twigs in which they live. Others are dark coloured and hide in the leaf litter on the ground and come up to feed only when the sun goes down.
Still others feed on poisonous plants and advertise their nastiness by being very colorful and remaining in open places where they are quite visible. Predators keep populations of butterfly caterpillars in check and thus prevent excessive damage to the vegetation on which they feed”.
Once the caterpillar reaches maturity, it wanders off in search of a suitable place to enter upon the next stage of its life cycle – pupation. Here the caterpillar attaches itself to a leaf or twig with a strong silk-like substance and changes into a chrysalis.
Some caterpillars wander quite far from the larval host plant and may even pupate on outside walls of buildings or even rock faces.
Although this stage appears quite inactive from the outside, it is a stage of great transformation where the internal tissues of the caterpillar are transformed into the adult butterfly.
Michael went on to explain that “as in the larval stage, the chrysalis has many enemies and to avoid them it adopts concealment and camouflage to keep them at bay. When the transformation is complete after a few weeks, the adult butterfly emerges from the chrysalis.
Initially the wings are very small and pliable. The butterfly pumps fluids stored in its body into the veins of the wings until they are expanded to their full size. Soon the wings harden and the butterfly is ready for flight”.
Michael said that although most butterflies require an hour or less to harden their wings after emergence, there are many species in which the females are mated immediately after emergence, even before their wings begin to harden The Common Grass Yellow is one such example.
He also went onto say that an interest in butterflies should be created among the younger generation so that they would get involved in conservation. Despite the inevitable loss of habitats of butterflies, there are still many things we can do to conserve butterflies.
One of the most effective is to provide habitats wherever possible in urban or rural areas. The planting of a few larval host plants in home gardens, for instance, is a very effective way of conserving butterfly populations.
For example, species of Citrus such as lime, orange and lemon are excellent sources of larval host plants for many swallowtail butterflies in Sri Lanka. Kiri Anguna or Thiththa Anguna (Wattakaka volubilis) are larval food plants for many species of ‘Tigers’, while Ehela (Cassia fistula) is the larval host plant for many species of white butterflies.
Many species of crotalaria and members of the bean family are also larval host plants for species of butterflies referred to as the Lycaenidae or ‘Blues’.
For adult butterflies, Golden Dew Drop, (Durantha repens), (Jatropa interogatum), Midi (Prenna alstonus), Lantana Kamara, Ixora coccinea, and Pentas are excellent sources of nectar.
These are also attractive garden plants that could be planted without sacrificing the aesthetic aspects of landscaping. Unfortunately, some of the larval host plants on which many of the Sri Lankan butterflies feed are yet not known.
On how long does a butterfly live, Michael said ” The egg stage of a butterfly lasts about 3-5 days. The larva lives from 10 to 30 days.
The pupal stage usually lasts 1 -2 weeks but can last for several months until conditions become favorable for the butterfly to emerge. Most adult butterflies live only 3 to 4 weeks though some may live only 2 weeks or as long as 2 – 3 months.
After emergence most butterflies fly in search of nourishment to attain sexual maturity as quickly as possible. As in the other stages of development, the adult butterfly also faces many dangers. Birds such as the drongoes and flycatchers readily attack butterflies in flight.
One strategy that butterflies employ to avoid birds is to not fly when birds are most active. This is one of the reasons why most butterflies wait until 9 to 10 am before taking flight. Once in the air they further insure themselves of safety by flying rapidly or in an irregular zigzag path.
Adult butterflies are also attacked by spiders, mantids and small lizards that wait for them at flowers, in disguise.
In nature, it is very rare for a butterfly to die of old age because they fall prey at some point in time as they age. As sad as the event may be, from the perspective of nature, a butterfly’s life is successful if it has reproduced and set the next generation in motion.
Michael said that everyone is familiar with the phenomenon of butterflies flying to Sri Pada during the April season (in fact, Sri Pada is also called Samanala Kanda, Butterfly Mountain).
This phenomenon is often called migration though it is really just a one-way movement of butterflies, unlike a true migration, which is a movement of whole populations to one place and then back.
There are two possible reasons for the movement of butterflies in large numbers. One: when butterfly numbers increase in a given area because of favourable conditions, they quickly deplete the food resources in that area.
Once the resource base declines, they often move to other areas in search of food. Two: It is also possible that this mass movement is a strategy to colonize new areas and thus expand the range of the species.
However, the greatest enemy of butterflies is man. We inadvertently destroy the habitats of butterflies by cutting down or fragmenting the forests that they live in, either for agricultural or industrial uses or simply for timber and firewood.
We use insecticides, which not only destroy the targeted pests but also destroy butterflies that are present in the area. The use of weedicides often destroys the larval food plants of butterflies that live in cultivated areas and prevents their development into maturity.
Michael is searching for and recording information on the life histories of many Sri Lankan species. He intends to use the information, which will be very useful, for the publication of a field guide on Sri Lanka’s butterflies.
He eagerly welcomes any information about butterflies from interested members of the public. He can be reached at email@example.com. Have a look at his web site www.srilankaninsects.net which has a wealth of information on Sri Lankan butterflies.
Photographs courtesy: Michael van der Poorten