Dr. Murai Éva szerk.: Parasitologia Hungarica 25. (Budapest, 1992)

and T. taeniaeformis larva increased gradually by weight category in females. It was mostly these three species which contributed to the value of the general prevalence. The explosion-like intensity of H. polygyrus infection was similar to that seen in males. In contrast with male mice, from females H. diminuta and H. muris-sylvatici were not recovered. Burdens of S. frederici and H. fraterna were not substantial in females either (Fig. 3). Microtus arvalis Seasonal variations As shown in the Table 3, the animals were collected mainly in the autumn; thus, no quantitative comparison was possible. However, it is worth noting thatA dentata, P. omphalodes and H. laevis showed a high prevalence in spring and winter in spite of Fig. 4. General prevalence and intensity of helminths parasitic in M. arvalis by weight category the small number of samples. In the present study, 7 cestode and 3 nematode species were recovered in autumn. Only three helminths, A. dentata, P. omphalodes and P. janickii were important from the point of view of the infection (see Table 3). Infection by H. laevis appeared a decrease (1.9 % for males and 6.0 % for females) in autumn, as compared to winter and spring samples. Males were parasitized by 1 or 2 specimens of helminths (75.0 and 25.0 %, respectively) and females by 1-3 (66.6, 22.2 and 11.2 %, respectively).