Dr. Kassai Tibor - Dr. Murai Éva szerk.: Parasitologia Hungarica 6. (Budapest, 1973)
The investigations were carried out on fresh or occasionally frozen animal bodies. To estimate the infections in the liver the developing cysts (point-like on the surface, embedded small cyst in tissues) or cysts containing developed larvae were considered. The larvae were identified on the basis of samples sent to Dr. É. MURAI (Hungarian Nat . Hist. Museum, Budapest). The age of the common voles was also considered in the investigation. The body length of specimens was taken as an Indication of age. The animals were divided into five groups as follows: below 75 mm (l), 75.1-85 mm (2), 85.1-95 mm (3), 95-1-105 mm (4), and above 105 mm (5) (see Fig. 2). Supported by the investigations of several authors (BASENLNA, 1953; SEBEK, 1959; SYKORA, 1959) the ages of these groups were considered to be (l) younger than 1 month (2), about 1-2 months, (3) about 2-4 months, (4) about 4-6 months and (5) older than 6 months. Considering the well-known problems of ageing I would like to emphasize the possibility of overlapping between the groups, therefore the frequency of strobilocerci examined in each age group and the true age of the animals is only approximate. From a synoecological standpoint the infestation of groups 1 and 5 can be truly estimated, because specimens of these groups are surely younger than 1 month or older than 6 months . Results and Conclusions l) Strobilocercosis was found generally in common vole populations from varied agricultural cultures; 222 (7.2 %) of 3097 Microtus arvalis specimens were infested (Tables 1 and 2). The degree of infestation in the more abundant population was greater than in the smaller populations. (It is shown in Table 1 that the abundance was directly proportional to the number of examined specimens.In Bük field the investigations were carried out during one population cycle. There would have been a peak year in 1971, but the population was decreased by controls carried out repeatedly in spring and autumn. Therefore the popula122
