O. Merkl szerk.: Folia Entomologica Hungarica 68. (Budapest, 2007)
very hot weather, which had begun rather early in the summer and was continuing also during the sampling period. Those 400 samples contained 21,009 individuals of adult flies. There were 300 samples taken in 2004. Suffering again from periodically bad weather, sampling days were on the 26 th and 27 th of July, as well as on the 4 th , 6 th , 17 lh and 19 th of August. Altogether 29,525 individuals were sampled in 2004 (Table 1). There were 300 samples taken in 2005 again. Weather conditions were ideal between the 25 th of July and the 3 r of August. Exactly 41 thousand individuals were captured in the last year of sampling. Originally we planned to sample approximately 24-hour old cow pats. Those ones contain the most species rich assemblages, and at the same time, their species composition seem to change rather slowly. The species, which are characteristic for the fresh dung, are still present, and, also the species, which utilise the older dung under the crust of the cow pat, have already been appeared. We had to change our plans under the hot summer conditions of the Hortobágy National Park. We sampled cow pats of 12 to 24 hours in order to follow the original aim. The 24 hour-old pats (laid morning, sun-heated during the daytime) have already had hard crust with beetle-made holes (for better ventilation). The age of cow pats was determined by observation on cows (as for defecation) and using my several decade long experience. The sampling device was developed based on our former experience on studying flies of cow pats and it is a result of several more of less successful previous trials. Our sampling device (Figs 1-2) was actually a very fine mesh, exactly conical net of 30-31 cm diameter and of a 70 cm depth. Its rim is formed from a 5 to 6 cm wide metal plate. For safety reasons we prepared three copies. An important part of our device is a tube, running around inside the rim, fixed at several places to the rim. The tube is with 18 small holes at a distance of 5 cm from each other, which are formed to emit air towards down and inside. The neck-point of the tube is with an Y-tube, whose third hole is connected with the flexible air tube. The air tube is blown by the user. The 12 to 24 hours old cow pat is covered quickly but carefully, starting with obliquely turned device from one side, after careful approaching of the selected pat. Blowing air into the tube will not allow flies to close the rim and so to crawl out under the rim and get free. On the other hand, air blowing will drive flies into air from the surface of dung and of the grass blades, and they continue their emergence in crawling upwards on net tissue by instinct. That is particularly so, if we move the rim gently horizontally, keeping it continuously pushed tightly to the ground. After all the flies have left dung surface, we drive all to the narrow end of the net by grabbing the rim strongly and making some strong sweeping moves, i.e. using our device like a sweeping net. Closing the apical part of the net with flies by our other hand, the end of net is immersed into 70% ethyl alcohol in a small dish, which kills dipterous adults immediately. The net is turned out and all the flies are washed into the alcohol. After sieving them by the partner, they are carried and preserved in 70% alcohol. That way they were ready for identification. There were cases, when one sample was taken over two small cow pats, but we do not think it important. It seems more important, that we really captured all the adult flies, that were present in a given moment on a cow pat. Actually, our method is not an estimation but a counting as regards individual cow pats.
