Jayanthi P. Edirisinghe

Biodiversity associated with an irrigated rice agro-ecosystem in Sri Lanka

Irrigated rice fields are temporary wetland agro-ecosystems, managed with a variable degree of intensity. A survey was carried out in Sri Lanka to document the overall biodiversity associated with this unique agro-ecosystem, using a combination of sampling techniques to document different groups of fauna and flora. The total number of biota recorded and identified from the rice field ecosystem during the entire study period consisted of 494 species of invertebrates belonging to 10 phyla and 103 species of vertebrates, while the flora included 89 species of macrophytes, 39 genera of microphytes and 3 species of macrofungi. Of the total species documented, 15 species of invertebrates and one weed species are new records to Sri Lanka. Arthropods were the dominant group of invertebrates (405 species), of which 55 species were rice pest insects, and 200 species were natural enemies of pest insects. The fauna and flora recorded from the rice field were observed to follow a uniform pattern of seasonal colonization and succession during successive rice cultivation cycles. The biodiversity of the irrigated rice agro-ecosystem interests both agroecologists and conservation biologists. Therefore, the integrated efforts of these two groups can result in the formulation of strategies based on biodiversity as an organizing principal in the sustainable management of the rice field agro-ecosystem.

Effects of artificial shade on attack by the mahogany shoot borer, Hypsipyla robusta (Moore)

Abstract 1 Swietenia macrophylla King (Meliaceae: Swietenioideae) provides one of the premier timbers of the world. The mahogany shoot borer Hypsipyla robusta Moore (Lepidoptera: Pyralidae) is an economically important pest of S. macrophylla throughout Asia, Africa and the Pacific. No viable method of controlling this pest is known. Previous observations have suggested that the presence of overhead shade may reduce attack by H. robusta, but this has not been investigated experimentally. This research was therefore designed to assess the influence of light availability on shoot‐borer attack on S. macrophylla, by establishing seedlings under three different artificial shade regimes, then using these seedlings to test oviposition preference of adult moths, neonate larval survival and growth and development of shoot borer larvae. 2 Oviposition preference of shoot borer moths was tested on leaves from seedlings grown under artificial shade for 63 weeks. A significant difference in choice was recorded between treatments, with 27.4 ± 1.5 eggs laid under high shade and 87.1 ± 1.8 under low shade. 3 Neonate larval survival on early flushing leaflets of S. macrophylla did not differ significantly between shade treatments. Larval growth rate, estimated by measuring daily frass width, was significantly higher for those larvae fed on seedlings from the high and medium shade treatments (0.1 mm/day), than the low shade treatment (0.06 mm/day). In laboratory‐reared larvae, the total mass of frass produced was significantly higher in the high shade treatment (0.4 g) than under the low shade treatment (0.2 g). 4 Longer tunnel lengths were bored by larvae in plants grown under high shade (12.0 ± 2.4 cm) than under low shade (7.07 ± 1.9 cm). However, pupal mass under low shade was 48% higher than that under the high shade treatment, suggesting that plants grown under high shade were of lower nutritional quality for shoot borer larvae. 5 These results indicate that shading of mahogany seedlings may reduce the incidence of shoot borer attack, by influencing both oviposition and larval development. The establishment of mahogany under suitable shade regimes may therefore provide a basis for controlling shoot borer attack using silvicultural approaches.

The ecological role of spiders in the Rice fields of Sri Lanka

ABSTRACT The purpose of this study was to examine the role of spiders in Sri Lankan Rice fields in terms of species composition and guild structure of spider communities. The abundance of spiders was also tracked in relation to insect pest density, crop age, weed cover in bunds, and agronomic practices. The study took place in Bathalagoda, Kurunegala District, Sri Lanka from November 1995 to March 1998, through five consecutive Rice cultivation cycles. A total of 59 species of spiders belonging to 13 families were recorded; 7 taxa (2 species and 5 genera) are new records for Sri Lanka. The largest family was Araneidae (12 species), followed by Tetragnathidae (11 species). Results show that spider diversity and abundance increases with the growth of the Rice crop, and that weed cover in the bunds (embankments) forms an important habitat for spiders, functioning as a reservoir and an alternate habitat during the fallow period. Hence, reduced slashing of weeds, together with the limited use of pesticides, would help to conserve and encourage the spider communities-natural predators of Rice insect pests.

Oothecal parasites of Periplaneta americana: Parasitization and development in relation to host age

Oviposition and development of Evania appendigaster and Tetrastichus hagenowii in live P. americana oothecae ranging in age from 0–44 days was investigated. E. appendigaster oviposited in oothecae of all ages but developed only in 0–28 days old oothecae. T. hagenowii oviposited only in oothecae 0–34 days old, but developed only in 0–28 days old oothecae. Oothecae parasitized by E. appendigaster were superparasitized only during the first 4 days after the initial parasitization. A single parasite emerged from each such oothecae, indicating that only one of the two ovipositions was successful. Oothecae superparasitized by T. hagenowii during the first 8 days of the initial parasitization, resulted in ca. 90 parasites from both ovipositions. Oothecae parasitized by each species of parasite were subjected to multiple parasitism by the other species. Oviposition of E. appendigaster in 0–25 days old oothecae, parasitized by T. hagenowii was ineffective as it resulted in the emergence of T. hagenowii only. Reparasitization of 0–36 days old E. appendigaster -parasitized oothecae by T. hagenowii within 0–32 days resulted in the development of T. hagenowii, but reparasitization thereafter was ineffective as only E. appendigaster emerged. Even though T. hagenowii is more efficient than E. appendigaster, in parasitizing and developing in different types of P. americana oothecae, under field conditions the two species of parasites contribute equally towards the natural control of P. americana.RésuméL’étude a porté sur la ponte et le développement de E. appendigaster et de T. hagenowii dans P. americana oothecae agées de 0 á 44 jours. E. appendigaster a pondu dans des oothecae de tous les aĝes mais ne s’est développer que dans celles qui ont été parasitées entre l’âge de 0 á 28 jours. T. hagenowii a pondu dans des oothecae agées de 0 á 34 jours mais ne s’est développées que dans celles agées de 0 á 28 jours. Les oothecae parasitées par E. appendigaster ont été “super parasitees” (parasité á nuveau) pendant seulement 4 premiers jours après la première ponte parasitaire. Un seul parasite est sorti de chacune des ces oothecae en montrant que seulement une des deux pontes a été réussie. Les oothecae “super parasitees” par T. hagenowii pendant les 8 premiers jours après la première ponte parasitaire ont donné naissance á environs 90 parasites provenant des deux pontes.Des oothecae parasitées par chaque espéce de parasites ont été s’ exposées au parasitisme multiple par l’autre espece. La ponte de E. appendigaster dans T. hagenowii parasité au stade oothecae agées de 0 á 25 jours était inefficace puisqu’on n’a obtenue que des T. hagenowii. Le parasitisme de E. appendigaster agées de 0 á 36 jours au stade de oothecae par T. hagenowii a donné naissance á des T. hagenowii pendant les 32 premiers jours mais ensuite le parasitisme était inefficace puisqu’ on a eu seulement l’apparation de E. appendigaster. Méme si T. hagenowii est plus efficace que E. appendigaster pour parasiter et se développer dans différants types de P. americana oothecae, dans les conditions experimentales les deux espèces de parasites contribuent également vers le contrôle naturel de P. americana.

First Reported Case of Fatal Stinging by the Large Carpenter Bee Xylocopa tranquebarica.

In the order Hymenoptera, bees, hornets, and wasps are well-known stinging insects whose envenoming can be fatal. Their stinging attacks are common in rural and forested areas of Sri Lanka. However, fatal stinging by the large-bodied carpenter bees is unreported. We report the first known case of a fatal sting by the large carpenter bee, Xylocopa tranquebarica, in a forested area in Puttalam (North Western Province) in the dry zone of Sri Lanka. A 59-year-old healthy male manual laborer accompanied by a fellow worker had been fixing a fence on a coconut estate bordering a forested area when a flying insect emerged from a dead tree trunk and stung him on his face. His coworker, who was watching the incident, killed the insect. The victim complained of immediate intense pain in the face and collapsed on the ground just after resuming work after 10 minutes of resting. He was found dead on admission to the hospital 90 minutes later. Autopsy showed normal coronary arteries and heart, but the lungs were slightly congested and contained secretions in the bronchi. Acute anaphylaxis was the most likely cause of death. This case presents the habitat, morphology, attack pattern, and the medical importance of large carpenter bees.

Diversity and distribution of termite assemblages in montane forests in the Knuckles Region, Sri Lanka

This study was conducted in the Knuckles Forest Region in central Sri Lanka, and investigated how termite species richness, abundance and functional group diversity vary in different montane forest types and identified the likely causes of this pattern. Termite diversity declined with increased elevation, with upper montane forests recording a single endemic species, Postelectrotermes militaris Desneux. Transect sampling in lower montane forests yielded 26 species, with a higher number from dry forests (22 species) than from wet forests (15 species). Species specificity also was high in dry forests (11 species) compared with wet forests (four species). Termite abundance did not show a distinct trend in dry and wet forests. Live-wood termites were present only in upper montane and high-altitude lower montane dry forests. Wet forests had a higher relative abundance (78%) but not species richness (40%) of soil and soil-wood interface feeders. In dry forests, both species richness (82%) and abundance (88%) of fungus-growing wood feeders were higher. The study suggests that key drivers of the species distribution pattern are low temperature and differing forest floor conditions. In the upper montane forest floor where earthworms dominate, wet soil and damp, woody litter riddled with beetles are not favourable for termites. In lower montane wet forests, moist, thick decomposing leaf litter and in dry forests, drier, relatively undecomposed leaf litter with many dry sticks and branches support species with specific food habits.

Sri Lankan ant assemblages on multiple use land

Abstract Due to a rapid increase in the human population much of the land in Sri Lanka is occupied by urban or village habitations. As such, the land around settlements is put to multiple uses that have a bearing on the fauna, the invertebrate fauna in particular. This short-term study examines the effect of different land use patterns on the ant fauna, a group increasingly used as indicators of habitat quality. The study area consists of a semi-agricultural site exposed to six land use practices. It is being used as a garbage dump, for cultivation of vegetables, banana and medicinal plants, as a tractor trail or footpath and also comprises areas left uncultivated, allowing grass to take over. The ant assemblages in these differently disturbed sites were studied for 18 months using 5 different methods of collection. A high generic diversity of ants was recorded comprising 22 species in 20 genera and 6 subfamilies amounting to 1/3rd of the ant genera and 1/10th of the species currently recorded for Sri Lanka. The majority of ant genera were common invasive species. Pheidole species were the most abundant ants in the study area as in other parts of the world. The highest species composition and diversity of ants were recorded from the garbage dump and species were evenly distributed in the grassland. The majority of ants were generalists in their food habits. The seed harvesters such as Pheidole spp., Solenopsis spp., Meranoplus bicolor were common in the grassland and footpaths. Certain ant species were confined to specific areas subjected to different land use patterns such as Pheidologeton sp. and Polyrhachis sp. to garbage dump, Tetraponera sp. to vegetable cultivations, Cardiocondyla nuda to footpaths and 2 species of Solenopsis and Cerapachys sp. to the grassland. Of the 5 different methods used in collecting ants, random hand collections yielded the greatest number of species. Ground nests of 10 ant species were located and each had its characteristic tumulus. The distribution of ant nests in the differently disturbed sites indicated that Camponotus nests are largely confined to the constantly disturbed sites such as the footpaths while Pheidole nests are common in all the areas. This study suggests that the high generic diversity observed is not an indication of habitat disturbances arising from different land use patterns, as only 6 genera were found to be habitat specialists.

Bee diversity in a semi-agricultural field - Sri Lanka

Abstract Semi-agricultural fields are part of the rural and urban landscape of Sri Lanka. This study examines the bees that forage and nest in a semi-agricultural field within the University Park. A year round study in the 11 ha site yielded 53 species of bees in 27 genera and 3 families. Their foraging plants consisted of 31 plant species in 17 plant families that included crops, weeds and trees. The majority of the bees were generalists with only a few confined to specific crops (okra and eggplant) and weeds (Ipomoea spp.). Nearly half the number of bee species at the site foraged on the weeds Sesamum rudiatum and Ipomoea mauritiana. Eleven species of bees nested at the study site. The rich bee fauna amounting to more than 1/3;rd the number recorded for Sri Lanka is attributed to the short-term cultivation of vegetables, the variety of flowering weeds present year round and the agronomic practices that favour nesting.

Rediscovery of Tetragonula praeterita after 1860: an unremarked common stingless bee endemic to Sri Lanka

Three species of stingless bees are documented from Sri Lanka, namely, Tetragonula iridipennis (Smith), Lisotrigona cacciae (Nurse) and the endemic Tetragonula praeterita (Walker). Tetragonula irdipennis is the well-known, widely distributed stingless bee in Sri Lanka while L. cacciae is a recent record of a tear drinking stingless bee from a single site in Sri Lanka. Until the recent rediscovery, T. praeterita was known only from its type specimen deposited in the British Natural History Museum, London with Sri Lanka as its locality and 1860 as its date of description. Location of several stingless bee nests, with an entrance different to that of the well-known T. iridipennis, led to the re-discovery of T. praeterita. Its nesting sites, characteristics of the nest entrance tube and the morphological and morphometric differences of the worker caste compared to those of T. iridipennis are presented in the paper. Eight species of stingless bees have been reported from the Indian subcontinent. It is possible that more than three species of stingless bees occur in Sri Lanka.

An Appraisal of Select Insect Taxa in Sri Lanka

The chapter provides information on diversity of selected insect taxa, namely, Isoptera, Aphididae, Thysanoptera, Formicidae, and Apidae, and of the rice fields in Sri Lanka. Isoptera of the island comprises 76 species in 29 genera and 4 families, with 33 species restricted to the island. Fauna is rich in wood-feeding foragers and fungus-growing wood feeders and poor in humus and soil feeders. Seventy-four species of aphids in 40 genera and 8 subfamilies have been documented with the exception of subfamily Anoeciinae. Host plant specificity is not so pronounced among aphids except for a few restricted to endemic plants and specific weeds. Thysanoptera are represented by 113 species in 63 genera. Among them are many cosmopolitan pests and several potential viral vector species with vegetables, ornamentals, and cut flowers harboring a large majority of thrips. Ants comprise 181 species in 61 genera and 12 subfamilies. Of special interest is the endemic SF Aneuretinae, solely represented by the relict ant, Aneuretus simony, now known to be widely distributed and abundant. Bees comprise 144 species of pollen bees and 4 species of honeybees in 38 genera and 4 families. Pollen bees are best known for their nesting habits as ground, hollow stem (leaf-cutter bees), and wood (carpenter bees) nesters. Among them are several specialist bees. Rice fields are rich in insects, due to their habitat heterogeneity, harbored 317 species, belonging to 19 orders and 104 families, during the two cultivation cycles, Yala and Maha.