O. Merkl szerk.: Folia Entomologica Hungarica 68. (Budapest, 2007)

Choosing both the object and the site, as well as of the modes and ways of elaboration including identification, are based on author's experience of several decades (PAPP 1971, 1976, 1992, etc.). The present paper is for information on device and way of sample collection, on details of our identification method, as well as on faunistical data; i.e. listing species names with total number of individuals and a comparison to former sampling. A quantitative ecological analysis of our data, particularly so for species abundance distribution, is given in another paper (IZSÁK & PAPP 2008). MATERIALS AND METHODS Sample collection Based on our previous experience, we had to choose a cow pasture, which had been grazed by cattle for several decades. During that long period of time populations of all those dipterous species have occupied cow pats, which are living on cattle pastures in Hungary. In addition, their populations have reached the best proportional sizes, which is characteristic in cow pat assemblages in Hungarian Great Plains. All these factors were considered when two pastures of the plains at Nagyiván (Hortobágy National Park) were chosen as study areas. Pastures around Új-kút [New well] and Mérges-kút [Angry/Poison well] are in a distance of less than 5 km from each other. In 2003 both sites, in 2004 and 2005 (as well as in 2002) only Új-kút area were sampled. Samples were taken from comparatively small areas of drinking places of cows. On these grounds the number of cow pats are much higher than that of the mean for that pasture. 50 samples per day were planned, but it was impossible to achieve this number within the given time limits on the other wide parts of the pastures due to the scattered pattern of the cow pats. Based on our former studies, our starting point was that the proportional sizes of the populations of the numerous Diptera species show the smallest fluctuations from the beginning of July to the middle of August. Consequently, samples were taken between July 25 and August 19 (in 2002 on the 23

rd of August). In order to avoid the effects of diurnal activity of flies, samples were taken in the hours prior and just afternoon, between 10 a.m. and 4 p.m. (N.B. an hour time summer change is performed also in Hungary). Some basic meteorological data (cloud cover, wind, air temperature just over ground in shade) were also recorded. Sampling was not possible for several days after heavy rains as a consequence of dilution of cow pats and possible damages to dipterous adults. Cloudy weather with high temperature or drizzling rain did not seem to influence sampling results, or the latter seemed to increase the activity of dipterous adults. In 2003 samples were taken twice in five-day periods: from July 28 to August 1 and from August 11 to 15. Weather was not continuously proper even in those periods (strong winds and also a heavy storm), so altogether only 400 samples were taken instead of the planned ten times 50 samples. The mean number of adults captured was somewhat less than that of the preliminary sampling in 2002 (1146 individuals/

15 samples), in all probability as a consequence of the