SPECIES COMPOSITION, BREEDING HABITAT DIVERSITY AND TEMPORAL VARIATION OF MOSQUITO LARVAE IN  KALUTARA DISTRICT, SRI LANKA.

Mosquitoes can breed in variety of environments and the knowledge on mosquito breeding site preference is important for planning effective mosquito control strategies. The present study was designed to investigate the species composition, habitat diversity and temporal  variation of mosquito larvae in Kalutara district, Sri Lanka. A larval survey was carried out once in every two months from January 2019 to December 2021 in 13 Medical Officer of Health (MOH) areas in Kalutara district. During the study 24,357 mosquito larvae belonging to 13 genera and 57 species were identified and  10 of them were vectors of disease. Aedes albopictus (Relative Abundance  =47.6) was the most prevelent mosquito species identified in Kalutara district. Aedes vittatu, Ae. albopictus, Armigeres subalbatus, and Culex quinquefasciatus were found in all MOH areas. Species richness was highest in Agalawatta area (number of species =26) and species diversity was highest in Panadura (Shanon Weiner diversity index (H) =2.211) and Palindanuwara (H =2.174) areas. There was no significant impact of urbanisation and rainfall on mosquito species abundance, species richness, diversity and distribution (p>0.05), However, there was a significant difference in the composition of mosquito larvae in urban and rural sites. In this study mosquito larvae were found in 48 types of aquatic habitats. Species richness was highest in rain filled artificial containers (number of  species =31) and species diversity was highest in stream margins (H =2.14). In addition to that, 20 species were idntified in phytotelmata habitats and among them the species diverity was highest in fallen leaves (H =1.91). Furthermore, 99 types of co-existence were observed among mosquito larvae including  vectors, non-vectors and predators. The two species Ae. albopictus and Ar. subalbatus were the frequently found co-existing species. Most of the mosquito larvae were found in neutral pH (n =24,077, 98%), and most of the mosquito species were found in stagnant (number of species =48), slightly turbid (number of species =50) aquatic habitats in shaded (number of species =50) environment. The volume of the breeding sites were significantly different among Aedes, Anopheles, Armigeres, and Culex species (p =0.000, F =18.785). Aedes vittatus and Cx. tritaeniorhynchus were the dominant larval species found respectively, in higher level (above 3m) and below the ground level (3m below) breeding places. Dickey-Fuller test showed that the time series data of the abundance of mosquito larvae was non stationary (p =0.013, t = -2.79) and Linear regression analysis and Perason’s correlation showed that there was a significant negative association between rainfall and abundance of Culex species (r = -0.674, p =0.002).Study revealed that, diversity and distribution of mosquito larvae were significantly different within the district and breeding site selection of female mosquitoes is also different from species to species. Also, the presence of the vectors of malaria, dengue, chikungunya, filariasis and Japanese encephalitis shows the potential risk of mosquito borne disease transmission within the district. This information, along with the epidemiological data can be utilised for implementation of effective mosquito control strategies in Kalutara district.