Understanding environmental factors affecting the timing and rate of animal development, as well as the factors that cause their effects, is of great importance. The purpose of this study was to establish the relationship between the onset and duration of the development from egg to pupal stage and water temperature in three black fly (Diptera: Simuliidae) species: Simulium (Simulium) reptans (Linnaeus 1758), Simulium (Byssodon) maculatum (Meigen 1804), Simulium (Boophthora) erythrocephalum (De Geer 1776). The study was based on surveys conducted between April and June of 1998–2010. The water temperature on the day of larval eclosion had no statistically significant impact on the beginning of development in any of the three species studied. The date when water temperature in the river reaches a certain value is important to the initiation of development in some black fly species. The present study revealed that the most important dates to the beginning of development of S. reptans black flies are when water temperature rises above 5° C, 7° C, and 10° C, while pivotal dates to the development of S. maculatum are when water temperature exceeds 4° C and 10° C. Water temperature most often exceeds the value important to the start of the development of these black fly species during March and April. The findings of the present study show that the hatching time of the two black fly species is also related to the mean water temperature in March and April. There were no statistically significant relations established between certain temperature dates and the beginning of larval development in S. erythrocephalum. Significant relations (p < 0.01) were found to exist between the duration of the development cycle from the first instar larva to pupa and the mean water temperature during the development period in S. reptans (r = -0.84; y = 53.088e-0.0806x, R2 = 0.70), S. maculatum (r = -0.82; y = 186.48e-0.1123x, R2 = 0.69) and S. erythrocephalum (r = -0.83; y = 58.768e-0.0652x, R2 = 0.70). The present study showed that the duration of development from the first instar larva to pupa in all the three black fly species studied was shorter when water temperatures during the development period were higher and longer when water temperatures were lower. The devised model of dependence between the duration of the studied black fly species' development and water temperature was verified experimentally.

This paper analyses the dependence of the first spring arrival dates of short/medium-and longdistance migrant bird species on climate warming in eastern Europe. The timing of arrival of the selected species at the observation site correlates with the North Atlantic Oscillation (NAO) index, air temperature, atmospheric pressure, precipitation and wind characteristics. A positive correlation of fluctuations in winter and spring air temperatures with variations in the NAO index has been established in eastern Europe. Positive winter NAO index values are related to earlier spring arrival of birds in the eastern Baltic region and vice versa-arrival is late when the NAO index is negative. The impact of climate warming on the bird's life cycle depends on local or regional climate characteristics. We tested the hypothesis that differences in climate indices between North Africa and Europe can influence the timing of spring arrival. Our results support the hypothesis that differences in first spring arrival dates between European populations occur after individuals cross the Sahara. We assume that the endogenous programme of migration control in short/medium-distance migrants synchronises with the changing environment on their wintering grounds and along their migration routes, whereas in long-distance migrants it is rather with environmental changes in the second part of their migratory route in Europe. Our results strongly indicate that the mechanism of dynamic balance in the interaction between the endogenous regulatory programme and environmental factors determines the pattern of spring arrival, as well as migration timing.

The impact of the North Atlantic Oscillation (NAO) on long-term air temperature fluctuations in Lithuania was studied for the period 1865 to 2000. Mean monthly values of 2 NAO indices (NAO-1, NAO-2) and air temperatures at 9 Lithuanian meteorological stations were used as references. Synoptic situations, as well as the mean sea level pressure (SLP) and 500 hPa geopotential height field of a total of 265 months, were analysed. NAO conditions were classified as positive, negative or neutral. Air temperature fluctuations in Lithuania during the cold period of the year (November to March) are positively correlated with fluctuations of the NAO indices. During periods of extreme NAO indices (| I | > ±1.5σ), a negative NAO phase is usually correlated (75 to 88% of the cases) to negative temperature anomalies, whereas a positive NAO phase is correlated to positive temperature anomalies. In the other cases, reverse impact of positive and negative NAO patterns, the relation between NAO phases and regional temperature anomalies is opposite or not detectable. Also, this study includes the analysis of atypical periods of NAO-like circulation: when positive NAO phase was related to negative temperature anomalies and negative NAO phase to positive temperature anomalies in Lithuania.

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Abstract. Warmer temperatures in the past 30 years have significantly influenced the seasonal development of insects throughout Europe. As a result of the outbreaks of black flies that have occurred in southeastern Lithuania since the 1970s it is hypothesized that this increase in black fly activity is due to the change in climate. To test this hypothesis the development of Simulium maculatum Meigen under different conditions was determined. This revealed that the time of hatching of S. maculatum eggs in Lithuania was influenced by winter air temperatures, especially those in March. Pupation in S. maculatum is associated with the increase in air and water temperatures that occur at the end of April and in May. The emergence of S. maculatum black flies occurs most often in May. At a water temperature of 13.2°C (1999), S. maculatum took 42 days to develop and half this time (21 days) when the water temperature was 18.8°C (2005). The number of black flies that emerged each year was determined by air temperature but unaffected by rainfall in June (either per month or per ten-day period).