Dr. Kassai Tibor szerk.: Parasitologia Hungarica 2. (Budapest, 1969)
other fleas from this host, and C.styx was found in only a single case on the stonechat (Oenanthe oenanthe L.), which occasionally nests in sites similar to the subterranean nesting cavities of the sand-martin. Thus we have the specific flea of a nest type which differs fundamentally from the nests of other species. It would be further proof of my assumption if C . s .styx were found in the similarly constructed nest of the bee-eater (Merops apiaster L.). These examples suffice to prove the merit of this type of investigations and to draw attention to my hypothesis . Finally, I should like to add some remarks concerning my work and future research. Though numerical data referring to individuals of coexisting species are available, I have discussed only cases of specific associations. In later communications I intend to consider, whose studying flea populations of a given host species, the numerical ratios and sex distribution sex of the parasitic species. A more intensive collecting of nests is also indicated, as well as the evaluation of the occurrence of fleas by seasons (YYSOTSKAJA, 1967), the comparison of flea species found on the hosts and their nests (JURIK, 1968), and demonstration of correlations between the development of fleas found on the hosts and their nests (ROTHSCHILD, 1967). One or more of these aspects have already been examined- by the abovecited authors and by others, without, however, all aspects being considered in the course of a given investigation. Many questions might be answered if it could be determined by laboratory investigations how far the flea species found in the samples show food preferences. Also, as already stated, I attach great importance to moisture, humidity, and temperature conditions affecting the several biotopes.The investigation of these latter seems to present most difficulties, since after the exposure of the nests the original microclimatic conditions can no longer exist. If a technical solution to this problem were assured, we would be much nearer a demonstration of the nestspecificity of flea species.
