IntroductionThe appearance of leishmaniasis cases has been correlated to the presence of Leishmania-transmitting sandflies. Various epidemiologic leishmaniasis transmission patterns are caused by ecological and environmental conditions that lead to sandflies population dynamics [1][2][3]. Sandflies life cycles are affected by climate variations due to natural processes, especially weather conditions (e.g., precipitation, temperature, humidity, etc.) [4]. Agricultural development and changes in climate conditions could favour new habitats for vector insects [5][6][7][8]. Increases in sandflies dispersion may lead to higher human-vector contact [9-13] and, therefore, higher risk of leishmaniasis transmission [3,14]. Zorilla et al. correlated the presence of cutaneous leishmaniasis to environmental and socioeconomic variables in population of Yaucano Valley in Perú, the adaptability of sandflies to the human en vironment may lead to an increase in the number of leish maniasis cases [15]. However, studies in dry climate regions have presented controversial results, such as a lack of correlation between climate variables and sandflies density [16,17]. Temperature increases may also affect sandflies populations [18][19][20]. Rodríguez et al. suggested that changes in ecological and climate conditions in Mérida, Venezuela from events such as flash flooding along stream beds at Mocotíes Valley may have affected the occurrence of leishmaniasis cases [7]. Thus, it is necessary to characterize the conditions that affect Leishmania-transmitting sandflies populations [4]. The goal of this study was to characterize the composition and structure of sandflies at endemic area of Mocotíes Valley in Mérida, Venezuela, and to determine the relationship between these characteristics with environmental variables. Materials and Methods Study areaThe selected area for this study was Zea Municipality State Mérida, Venezuela located in the southeastern quadrant of the State (latitude 8º20'20'' to 8º33'00'' , longitude 71º42'10'' to 71º49'20"), the transition zone between Mocoties Valley and the southern edge of Lake Maracaibo, located between the mountains and Escalante and Guaruríes rivers. An area of 135 km 2 at 600 m above sea level (ASL) has lower mountain tropical rainforest vegetation. The annual average temperature is 22ºC, with annual rainfall of 1390 mm and comprises two Parishes, El Caño Tigre and Zea. Environmental variablesThe altitude of each sampled location was recorded with an altimeter. Measurements were grouped into two altitude ranges: below 600 m ASL, corresponding to Caño El Tigre Parish, and above 600 m ASL, corresponding to Zea Parish. Temperature and relative humidity (RH) were measured with a digital thermo-hygrometer. Four measurements were measured made during a 1-hour period between 19:00 and 20:00. Two average temperature ranges, below 25°C (19-25°C) and above 26°C (26-33°C), and three RH ranges, below 60%, between 60% and 80%, and above 80% were defined. AbstractBackground: Sandflies distribution is associat...