International Research Symposium on Pure and Applied Sciences (IRSPAS)
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Item Diversity of Yala season diurnal ant community in two selected rice fields in the Wet Zone of Sri Lanka(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Wickramasinghe, W.P.C.S.; Dias, R.K.S.Studies on the ant communities of Wet Zone rice fields in Sri Lanka are scarce and the present study was conducted to determine the diversity and species composition of ants throughout Yala season. Worker ants were sampled within two, almost similar, rain-fed rice fields (18 x 20 m) in Mahadarawa, Gampaha District from February to September in 2017 encompassing post-harvest, seedling, tillering, flowering and mature grain stages. In each rice field, pitfall trapping (20), honey baiting (20) and hand collection (15) were employed along a 20 m line transect during daytime. The collected ants were preserved in 85% ethanol and identified to the possible taxonomic levels in the laboratory using the relevant references. Air temperature and light intensity varied between 32-360C and 14478-19983 Lux m-2, respectively. Eleven ant species, Anochetus graeffei Mayr, Anoplolepis gracilipes Smith F., Camponotus compressus Fabricius, Carebara diversa Jerdon, Diacamma rugosum Le Guillou, Meranoplus bicolor Guerin-Meneville, Monomorium floricola Jerdon, Odontomachus simillimus Smith F., Paratrechina longicornis Latreille, Tapinoma melanocephalum Fabricius and Tetramorium walshi Forel in 11 genera of 4 subfamilies, Dolichoderinae, Formicinae, Myrmicinae and Ponerinae were recorded from the two rice fields. The most speciose subfamily was Myrmicinae whereas Dolichoderinae contained only a single species. Species richness observed for seedling stage and post-harvest stage-2 was 9, while 11 species were observed on the other occasions. Higher Shannon-Wiener Diversity index value (H’= 2.093) was observed for tillering stage than that of the seedling stage (H’= 1.764). The highest mean percentage frequency of occurrence was observed for C. compressus followed by T. melanocephalum while A. graeffei had the lowest value. Significantly higher frequencies of C. compressus and T. melanocephalum were observed (Chi square test, p<0.05) at the ‘Field 1’ and ‘Field 2’ on all occasions. A diverse ant community consisting of 9 permanent inhabitant species occurred at the two fields irrespective of the presence of both wet and dry conditions. Carebara diversa was a nuisance to farmers because the workers carried away germinated rice seeds from the paddy fields. It appeared that O . simillimus was a predator of the rice pest, Gryllotalpa orientalis Burmeister (Oriental mole cricket).Item New records of ant taxa (Hymenoptera: Formicidae) in four subfamilies from Sri Lanka.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Dias, R.K.S.; Wackhoo, A.A.; Akbar, S.A.Ants belonging to 11 subfamilies have been recorded from Sri Lanka. In subfamily Amblyoponinae two genera, Stigmatomma and Myopopone, were previously known from the country. We report here new records of two genera and four species to Sri Lanka, deposited at the ant repository of the first author’s Department. Ants were identified using a Low Power Stereo-microscope at suitable magnifications with reference to relevant literature. A Prionopelta Mayr, 1866 worker in amblyoponinae was identified in the samples collected by soil sifting in November, 2004 from “Pompekelle” (PF), Ratnapura. Among the amblyoponines, Prionopelta is characterized by the possession of narrowly triangular mandibles with only 3 teeth in the masticatory margin, with the smallest median tooth; no space between the masticatory margins and clypeus when mandibles are fully closed. Dorylinae was redefined by amalgamating several subfamilies and resurrecting some generic names recently. Specimens of the doryline genera, Aenictus, Dorylus and Cerapachys recorded previously from Sri Lanka were re-examined using a Low Power Stereo-microscope with reference to the recent resurrection of generic names. Lioponera Mayr, 1879 was identified among the doryline workers collected from Kumbukwewa Forest, Kurunegala District in February, 2010 and a coconut plantation in Ihakuluwewa, Polonnaruwa District in November, 2008. Both genera are widely distributed across tropics but this the first record of Prionopelta and Lioponera to Sri Lanka. the first record of the genus to the country. Amongst dorylines, Lioponera has a pair of compound eyes and 12-segmented antennae and lacks the promesonotal suture; mesosoma is distinctly marginate dorso-laterally, mesotibia has a single spur and the metacoxa has a postero-dorsal cuticular flange that forms a vertical lamella. Also, ant species, Stigmatomma belli in subfamily Amblyoponinae collected from PF in March, 2004, Ooceraea alii (Bharti & Akbar, 2013) in subfamily Dorylinae collected from a coconut plantation in Ihakuluwewa, Polonnaruwa District in November, 2008, Camponotus opaciventris Mayr, 1879 in subfamily Formicinae collected from Watinapaha, Gampaha District in April, 2017 and Protanilla concolor Xu, 2002 in subfamily Leptanillinae collected from Anuradhapura Sanctuary in Anuradhapura District were identified as new species records to Sri Lanka.Item Discovery of three new Tetraponera species (Formicidae; Pseudomyrmecinae) from Sri Lanka.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Dias, R.K.S.; Udayakantha, W.S.; Thotagamuwa, A.; Fernando, K.S.S.D.; Madushani, N.Tetraponera F. Smith is the sole genus of subfamily Pseudomyrmecinae recorded from Sri Lanka and very little is known about the diversity of the arboreal genus in the country. Nests of Tetraponera species were collected by checking the worker trails and locating them followed by severing the nests from the host trees. Colony members in (i) a nest in a cashew tree branch from Delgoda (7º 00.395´N and 80º 00.96´E) Udupila in Gampaha District in March, 2015 (ii) three nests of Tetraponera from two jack trees in the premises behind the Department of English language Teaching (6º58´ 35.94" N and 79º54´ 58.8"E), University of Kelaniya in March, 2015 and (iii) a nest in a dry rubber branch from Gulanakanda (6°35'01.7"N 80°00'36.7"E), Bombuwala, Kalutara in August, 2016 were preserved in 70 % ethanol for the identification and listing of Tetraponera species. Fifteen morphometric parameters of each adult caste of each species, if present, were measured using a calibrated micrometre eyepiece fixed to a stereo-microscope and total length of the adult castes were measured by a ruler in mm scale, which was kept under the stereo-microscope. Cephalic Index (CI=HW/HL), Scape Index (SI=SL/HW) and Relative Eye Length (REL=EL/HL) were also calculated. Worker ants were identified to the species level refering to the relevant literature; T. extenuata Ward, T. microcarpa Wu and Wang and T. modesta (F. Smith) in Tetraponera allaborans-group were identified from the nests (i), (ii) and (iii), respectively. Black or dark brownish black worker with the contrasting brownish orange post-petiole, tibiae, tarsi and scapes, taller and more slender propodeum and more convex and soft-edged pronotal margins characterized T. extenuata workers. Workers of T. microcarpa were of black or brownish black, with lighter brown petiole, post-petiole and appendages, bidentate median clypeal lobe, short and broad profemur and quadrat-shaped propodeum. Small size, orange-brownish colour of the body with lighter colour appendages and relatively slender profemur characterized T. modesta workers. Colony demography of each nest recorded by counting the number of each adult caste with the naked eye and that of larvae, pupae and eggs under the stereo-microscope indicated that workers generally had the highest percentage abundance whereas eggs or larvae were also present in higher percentages. Very low percentage of dealate queen was observed in each nest. Four Tetraponera species, T. rufonigra (Jerdon), T. allaborans (Walker), T. nigra (Jerdon) and T. nitida (Smith) recorded previously from Sri Lanka rose to seven with the current findings. A taxonomic key that distinguish all Tetraponera species recorded from Sri Lanka is prepared with the colour images to facilitate quick identification of workers of each species.Item Effects of kerosene and citronella oil on the worker ants of Tetraponera rufonigra Jerdon (Formicidae, Pseudomyrmecinae), a medically important ant species, in tropical Asia(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Dias, R.K.S.; Fernando, K.S.S.D.Serious medical conditions due to sudden outbreaks of Tetraponera rufonigra and increase of its stings in urban localities were reported recently in Sri Lanka. Control methods appropriate for suppressing T. rufonigra workers in such situations were investigated using kerosene or citronella oil in the laboratory. Toxicity tests were conducted with appropriate control experiments and in three replicates, by applying 10 μl, 12 μl, 14 μl, 16 μl, 18 μl and 20 μl of citronella oil on dorsal prothorax of each of the acclimatized ten workers used in each treatment. Number of dead ants observed with each treatment was recorded after 10 minutes of each application. Probit analysis performed with the percentage mortality of workers resulted 6.38 mg/mg body weight of ant of citronella oil as LD99 of the workers. For field simulating experiments, citronella oil containing (100%) sprayer bottle and a common hand sprayer were bought and spray volume of each sprayer was calculated. Increasing volumes 0.6 ml, 1.2 ml, 1.8 ml, 2.4 ml and 3.0 ml of kerosene or 0.64 ml, 1.28 ml, 2.56 ml, 3.84 ml and 5.18 ml citronella oil based on the calculated spray volumes, were applied separately to ten acclimatized workers in a plastic bottle in three replicates; time period until ten worker ants died since spraying was recorded for each treatment. Appropriate control set up was maintained for each treatment. Spraying of 3.0 ml of kerosene or 5.2 ml of citronella oil, as minimum volumes, is recommended for the temporary suppression of ten worker ants.Item Arboreal ant assemblages (Formicidae) and importance of Oecophylla smaragdina (Fabricius) occurrence in a wet zone cashew field in Sri Lanka(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Dias, R.K.S.; Perera, A.P.S.Many ant species (Hymenoptera, Formicidae) have the potential to control herbivore abundance, reducing the plant damage while increasing plant growth, reproduction and yield in agro-ecosystems. Ant assemblages on six cashew trees in Delgoda, Gampaha District were recorded throughout three phenological phases by visiting the field six times from March to June in 2015. Seven to 15 baited traps were set 25 cm apart on the branches of each small, medium and large tree and collected after three hours. Worker ants seen on the main trunk and four major branches of each tree during a five minute period were hand-collected 5 to 9 times from small to large trees on each occasion. Collected ants were preserved in 70% ethanol, identified and listed. Number of Oecophylla smaragdina (Fabricius) nests observed on the same trees was recorded from April to June in 2015. The materials carried by O. smaragdina workers on cashew tree branches were also collected, preserved in 70% ethanol and identified to the possible levels using a Low Power Stereo-microscope. Fourteen ant species in five subfamilies were recorded. Species richness observed on each occasion ranged from 7 – 11 while O. smaragdina was the only species on all cashew trees. Nests of the species of O. smaragdina were observed only on one or two large and medium-sized trees. Various plant and animal materials carried by O. smaragdina workers confirmed that the species is an omnivore and a generalist predator. Presence of ant assemblages on cashew trees in the absence of any insecticide application in the current cashew field may have contributed to an observed absence of serious damage by cashew insect pests elsewhere.