in Sri Lanka - Ministry of Environment

Threats to butterfliesThe most significant threat to the butterfly fauna of Sri Lanka is the disappearance anddegradation of forest, grassland and coastal habitats due to human activity. In the wet zone,the greatest concerns include the ever-increasing illegal encroachment of human settlements,the illegal felling of trees for timber and firewood and the illegal expansion of tea and rubbercultivations into the protected forest reserves. In the dry and arid zones, the situation is similar,though it is the illegal cultivation of rice and other crops that threatens the butterfly habitats.The coastal habitats of butterflies are threatened by a more recent phenomenon: the rapiddevelopment of hotels and resorts in many near-pristine areas of the coast.In addition to these general threats, there are specific ones. For example, the introduction ofthe thorny non-native tree, Prosopis juliflora, to the arid zones has eliminated the native flora,including the larval food plants and nectar sources of many species of butterflies, which wereonce common in that eco-system. In the southern arid zone, the incursion of Prosopis will havea dramatic impact on the survival of Tarucas callinara, which is entirely restricted to the coastalarid zone of the south and south-east. The situation in Mannar and Arippu is the same wherethe most affected species is Junonia hierta, a species entirely confined to the coastal belt ofthe arid zone of the north and north-west. Several other butterfly species of the arid zone (e.g.Ixias pyrene and Colotis amata), which are also found in the dry zone, have undergone localextinctions in places where Prosopis has replaced the native thorn scrub.The Knuckles Conservation Area also faces several specific threats. Pinus caribaea has becomenaturalized and is invading the natural grasslands, which are the habitats of butterflies suchas Baracus vittatus, Eurema laeta, E. brigitta, and Mycalesis mineus. The native undergrowthof much of the forested areas has been taken over by the cultivation of Elettaria cardamomomand the naturalization of Cestrum nocturnum. In addition, the spread of these two speciesalong streams as well has displaced much of the native vegetation. In particular, Asystasiachelonoides and Pseuderanthemum latifolium which are larval food plants of Doleschalliabisaltide have declined and continue to disappear in many stream habitats. Similarly, severalspecies of Strobilanthes, which are the larval food plants of Kallima philarchus have alsodeclined with the consequent adverse effects for the butterfly.The threat faced by Symphaedra nais in the Nilgala-Bibile savanna grasslands is not oneof invasion by foreign plant species, but one of yearly forest fires deliberately set by peopleliving in the area and uncontrolled utilization of its food tree. The fires are set to allow for newgrowth of grass for improved grazing by animals and to promote flushing of the “beedi” tree,Diospyros melanoxylon. The newly matured leaves of this plant are used by the local peopleto manufacture a type of local cigarette called “Beedi”. These maturing leaves are also usedby the larvae of S. nais as their food source. The harvesting of these leaves destroys ova andlarvae in large numbers while adults perish under the fires set to the forests. The fires alsoprevent young trees from developing into mature seed-bearing trees. At times, entire branchesare lopped off mature trees to make collecting the maturing leaves easier. These activitiescoupled with the dying off of mature trees will result in a deficit in the seed bank for the futuregenerations of D. melanoxylon. The direct effects of fire, the harvesting of leaves and the likelydisappearance or drastic reduction of D. melanoxylon from this habitat do not bode well for thesurvival of S. nais.28