Seasonal Dynamics of Activity of Horseflies (Diptera, Tabanidae) in Pskov Province

Abstract

We studied the seasonal dynamics of flight activity in horseflies (Diptera, Tabanidae) belonging to 30 species from 6 genera. The results show that the abundance of horseflies is largely controlled by abiotic factors, such as temperature and relative humidity. Horseflies start their flight activity at an air temperature not lower than +15°C and relative humidity not lower than 57%. There are species-specific differences in the seasonal pattern of activity. Depending on the season when activity commences, the horseflies studied can be divided into spring species (end of May), early summer species (beginning of June), and summer species (beginning of July). We attribute this variation in the timing of adult emergence to different temperature and humidity optima for larval and pupal development in different horsefly species. A routine is proposed for estimating the long-term seasonal dynamics of flight activity of horseflies with the use of weekly and monthly mean temperatures, relative air humidity, and the sum of degree-days. In a similar manner, the flight activity pattern can be projected into the future.