Dr. Murai Éva szerk.: Parasitologia Hungarica 22. (Budapest, 1989)

A field trial was carried out to obtain data on the effect.of diflubenzuron on the fly community in cattle dung in calf and cow houses. MATERIAL AND METHOD An aqueous solution of diflubenzuron was sprayed once on a calf house, and a cow barn of a dairy farm at potential fly breeding sites known a previous study (DEMÉNY 1989). Dimilin^ WP-25 was used at 0.1 % concentration in the calf house, and at 1.0% concentration in the cow barn at rates of 0.7 g/m

2 and 0.5 g/m

2 effective substance, respectively. Fly breeding sites covered with thick straw could be saturated only with far more volume of liauid in the calf house as compared to the cow barn; this was why there was tenfold difference between concentration of working solutions used in the two places. Working solutions were prepared on the spot just before the treatment carried out by a five-litre atomizer. Three hours later 18 and 7 samples were taken from the treated litter in the calf and cow stable, respectively. Floor and air temperatures were measured simultaneously. The samples were put into rearing pots and kept under laboratory conditions for rearing the fly imagoes (DEMÉNY 1989). Samples taken from the same sites on the previous day served as control. The imagoes that emerged were collected three times during an incubation period of eleven weeks, and identified according to the works of MIHÁLYI (1972, 1975). After removal ofthe samples from rearing pots, they were checked for pupal shells and praepupae under intense light. The diversity index of the fly communities was calculated by the Shannon-Wiener formula (SOUTHWOOD 1978). where p. is the proportion ofthe i-th species, and there are a species. The evenness (E) of the diversity was calculated by the formula of s log s RESULTS AND DISCUSSION Calf hous

e Results of fly rearing from litter samples taken before and after spraying with diflubenzuron are shown in Table 1. The compound made a definite influence on the species composition of the fly community. The number of species, the Sh.-W. diversity index, and the evenness related to litter samples were considerably lower after the treatment, however, the total number of Diptera almost doubled. Within this, the number of Musca domestica and Copro ica hirtula imagoes increased. This could have resulted from the presence of many late stage larvae or pupae in the samples which were exposed to diflubenzuron. These immature stages are less, or not at all, susceptible to the compound (ABLES et al. 1975; FARKAS and SOUNTHONE 1985). On the other hand, the dispersion of fly immature stages at the breeding sites is never equal, and this has a great influence on the number of fly imagoes that can be reared from litter samples. After removal of the samples 202 Muscid pupae with doubled and/or abnormally thin shell were found among the 254 ones. Fat body of the larvae was usually found as dry, calcified material within the pupal shells. s H E s