Come back pretty butterflies, come back

This is the Sri Pada season. In the old days, many would recall seeing thousands of butterflies swarm the skies, making amber clouds, all moving in one direction. It is believed they would fly toward the holy mountain of Sri Pada as this mass movement coincides with the pilgrimage season.

But there are fewer swarms of butterflies today, especially from urbanized areas mainly due to habitat destruction. The only way to get them back, experts believe, is by restoring their lost environment. Drawing the younger generation under their conservation umbrella, the Wildlife and Nature Protection Society (WNPS) recently initiated a programme to restore butterfly habitats in schools. The project aims at establishing over 100 Butterfly Gardens in schools around the country and raising awareness on the need to protect them.

Butterflies require two kinds of plants to survive. Their larvae - the caterpillars- that feed on leaves need a host plant. The plants with nectar-bearing flowers are required by adults to feed on. Different species of butterflies have different preferences of nectar, in both colours and tastes. By planting these particular bushes and trees, anyone can create a butterfly-friendly habitat.

Some of the plants that host larvae include Cassia (thora), Lime, Katurumurunga, Ehela, Olinda, Sapsanda and Karapincha. Some easy to plant nectar plants are Balunakuta, Adenahiriya, Hibiscus (shoe flower) and Ixora.

The WNPS project aims at planting identified plants in designated plots in the selected schools. WNPS will also train the students and provide host plants and feeding plants wherever possible. The essential tools for maintaining the garden are also donated. "The enthusiasm shown by the schoolchildren is quite encouraging. Even small children want to take part in this exercise," said Douglas Ranasinghe, President of WNPS.

Twenty-five students from each school are trained in identifying the butterflies and to ensure maintenance of the gardens. A plant nursery will also be maintained in these schools. Exceeding its target, WNPS established 105 Butterfly Gardens in 10 districts in Colombo, Kandy, Galle, Ratnapura, Polonnaruwa, Kurunegala and Anuradhapura.

As the second phase of the project, the team will visit each school to review and enhance the conditions of the butterfly habitat. The project was done in collaboration with the Central Environmental Authority (CEA). The National Zoological Gardens, Laxman Weerathunga and Dr. Michael van der Poorten also helped the programme as consultants. The World Conservation Union - IUCN supported the project financially.

WNPS expects this project will spur students to turn their own backyards into butterfly gardens. Then their friends and neighbours may follow.

Mystery surrounds butterfly migration or the mass movement of butterflies in a particular direction, a phenomenon that usually happens after the first rain following a long dry spell. It is sometimes the onset of the south-western monsoon (March/April), which coincides with the Sri Pada season. But butterfly swarms do not necessarily move toward Sri Pada.

Butterfly expert Dr. Michael van der Poorten says there are several theories behind this mass movement of butterflies. A butterfly may lay 100 - 200 eggs, but out of these, only a small fraction (two to five) manage to reach adulthood. Predation and parasitism eliminate the vast majority of the eggs and larvae. Butterfly pupa has the amazing ability to remain dormant for about 6 months during dry weather. So if the outside is drier, the butterfly pupa can wait until better conditions arrive.

In the absence of butterflies, the population of parasites also drops. The drier period might also reduce the predatory population. Once it rains, butterflies from these preserved pupae will emerge. Having a shorter lifetime, they breed quickly and lay eggs. And if the parasitic load is low, most of these eggs reach adulthood successfully. Instead of 2-3 butterflies that used to reach adulthood out of 200-300 eggs, the population now increases several-fold and butterflies flourish.

This sudden influx quickly exhausts the resources in one area and the butterflies start moving in search of new ground. This is what makes the mass movement which lasts only a few weeks. But this theory is also challenged on the grounds as to why butterflies ignore the plants on their way and continue flying in one direction.

Another theory is that they move through an ancient route that their ancestors travelled. However, more research is needed to study the butterfly's movement patterns.