Dr. Kassai Tibor szerk.: Parasitologia Hungarica 2. (Budapest, 1969)

finite preference for artificial nesting boxes,where the squirrel fleas (

M.sciurorum

) living on the dormice may be found together with the fleas of avian species which had previously nested there. This association will not be considered as it is the result of human interference and not natural. Nor do I wish to discuss the various common occurrences of flea species to be found on our domestic animals. Discussion From the foregoing data of observed coexisting flea species, an attempt will be made to answer the problems raised in the introduction

. 1. The following systematic relationship can be established between flea species occurring together on a given host or in its nests: the members of the populations belong to various families and genera in.... 42.1 fo of cases; the same family in 18.4 ^ of cases; the same family and genus in 39.5 i° of cases. Taking into consideration that half the species of Hungarian Siphonaptera belongs to the family Hystrichopsyllidae and nearly one-third to the genus Ctenophthalmus - whose members are the most commonly occurring fleas - one can safely conclude that the apparent connections between species occurring together stem more from the composition of the fauna than from any inclination of closely related species to form certain types of association. There is as yet no justification for relating the specific composition of mixed populations to any nearer interrelationship. 2. I sought in vain to explain the inclination of the species to live together. Nor is there any reason to suppose an interdependence of the' species: they derive no advantage or disad-