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

times the year's average (Fig. 2), i.e. at a time when dormice are still absent from nest boxes (winter sleep), or are just beginning to occupy them in some places. A certain increase in population abundance takes place during the autumn months, when the abundance curve is considerably affected by the species C. sciurorum. Bird fleas are also the most abundant in April and attain a second peak in October, but are present throughout the year. Mammalian species were found fairly irregularly in nests, with a maximum in September-October (AT. turbidus). The seasonal pattern of flea prevalence in M. avellanarius (for all the months) is practically identical with that in Glis glis, the only difference being in prevalence values. 200 T 180 -160 -140 -V 120-a I 100 -u e 80 -60 -40 .20--| : I oJJ Il 1

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I I I II III IV V VI VII VIII IX X XI XII Month Fig. 2. Flea occurrence in dormouse nests during the year, expressed in terms of intensity DISCUSSION A comparison of the flea fauna in dormice The flea fauna of various species of dormice is not identical, particularly as regards the quantitative representation of their basic ecological groups. (For lack of material, Dryomys nitedula is not evaluated here; similarly also certain unspecified dormouse nests are left out of acccount). In this respect, the difference between Glis glis and Muscardinus avellanarius is evident. The prevalence and dominance of C. sciurorum, bird fleas and fleas of small mammals are shown in Tables 2 and 3. We attribute this difference to the varying degree of aggressiveness of the two hosts. Glis glis is incomparably more agressive, driving away other hosts (partricularly birds) from its neighbourhood, and destroying nests if nest boxes are occupied by other hosts. Its own nests, either standing by themselves or built on those of other hosts, are for the most part more humid, with a thicker layer of detritus which creates suitable conditions for the developing stages of fleas (probably for C. sciurorum in particular). Nests