S. Mahunka szerk.: Folia Entomologica Hungarica 54. (Budapest, 1993)

in cattle populations where regular sprayings were applied against dipterous pests; i.e. sprayings did not change the basic ratios in the dominant dipterous populations (cf. Papp and Garzó 1985). As it is well known those sprayings kill all specimens of Haematobia since almost all imagos at a given time are present on the bodies of cattle. At the same time only those specimens of Musca autumnalis are killed winch are actually on the bodies of cattle, which is a minute ratio of the whole population of that species (i.e. 0.1-0.2 % plus those specimens which land on cattle while the compound is still in a quantity enough to kill them). A surprisingly high number of Musca autumnalis and a good number of Musca tempestiva were collected on the bodies of sheep at Polgár. It is possible that those specimens are from the pastures of cattle (rather distant from this sheep pasture) but it seems likely that at least a part of those specimens emerged from sheep dung on their pasture. Flies reared from samples of cow pats (Table 2) are interesting indeed, particularly so for the species emerged from the September samples (Table 2). Though the number of specimens are lower than in the summer samples owing to the cool and rainy weather in September. It seems most remarkable that specimens of two species of the ceratopononid genus Culicoides were reared from cow pats for the first time in Hungary (as Nibaruta (1982) did it in Belgium), which are very important from a point of view of the veterinary science as they are transmitting viral diseases. It is worth mentioning that a species of the limoniid genus Limonia was reared from cow pats (cf. Nibaruta 1982) as well as one specimen of the drosophilid species Scaptomyza pallida (Zetterstedt, 1847); it was made for the first time. An analysis of the flies emerged from eight cow-pat samples collected on the 20th of June at Mózes-major is rather illuminating from a special point of view. It is well known that females of Musca autumnalis lay eggs rather unevenly on cow-pats (cf. e.g. Papp 1971) as for space and time. If weather is unsuitable females do not lay any eggs and since fresh cow pats lose most of their odours attractive for Musca autumnalis females during one day (and night), one day later a given cow-pat is far less attractive for them than the fresh ones. Our samples represent such a situation. There were only 3 specimens of M. autumnalis among the 3,500 specimens of flies reared, contrarily to the fact that the abundance of this species is 10 to 15 % among the flies emerge from cow pats in Hungary in the summer months. The results of rearing can be regarded as results of an unplanned „natural trial" for the situation when Musca autumnalis, whose larvae play the most important role in the rapid decomposition of cow pats on pastures in summer, would be exterminated. A train of thoughts to evaluate these results may be the following: The semiliquid substances of high nitrogen content of the cow pats, which are cementing the undigested macroscopic grass particles when dried, can pass more or less completely through the guts of dipterous larvae (and thus disintegrating them) if the amount of larvae developing there is about 5 per cent of the weight of cow pat (measured in dry weights, see Papp 1971). We found formerly that the activity of about one-fourth to one-third of that amount of larvae (i.e. a ratio of 1.25 to 1.7 %) is required to a rapid disintegration of cow pats on pastures in the summer months. According to our estimate (based on the papers of Papp (1971, 1976) and of Papp and Garzó (1985) only the production value of the sample No. 1 is high enough to this requirement (1.40 %), and, production values of two other samples (Nos 2 and 6) approximate that value (0.89 %, 0.86 %, see Table 2). For the moment we can propose only a carefully planned and precisely realized series of experiments in order to know more on the parallel ways of decomposition. A hypothesis that in lack of the larvae of Musca autumnalis the larval populations of the other obligate coprophagous species are able to take over the role of the M. autumnalis larva is to be tested and should not to be rejected (cf. Papp and Garzó 1985). The species composition of the dipterous assemblages on sheep dung does not seem less rich than that of the flies on other dung (Table 3). Although no species was found which was not included in Papp's (1992) table for dipterous species developing in pasture dung in Hungary, it is important to have data from localities very much different from those dry