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Some aspects ofthe host:parasite relationships between adult blackflies (Diptera; Simuliidae) and larvae ofthe water-mite Sperchon setiger (Acari; Hydrachnellae) in a small chalk stream in southern England T. GLEDHILL, JUDITH COWLEY and R. J. M. GUNN Freshwater Biological Association, River Laboratory. Warehatn. England.SUMMARY. In Bcrc Stream three species of adult simuliids, 5. ornatum.S. eqiiinum and 5. angustipes were parasitized by Sperchon setiger larvae. Trapped adult 5. ornatum were more often parasitized than corresponding adults of 5. eqttimtm. The lower 95^1 confidence limits were used as an indication of the relative importance of the statistically signiricant differences and were high {10.4-33.6'^). Laboratory experiments on the occupation of host pupae by pre-parasitic5/7erc/io«5e/iger larvae also indicated that pupae of 5. ornattim were more often occupied than S. eqiunum. This was confirmed by tests on the difference in percentage occupation of more than 4000 held-collected host pupae. In tests that indicated a significant difference in percentage parasiti/alion between the sexes of the three host species, females were more t)ften parasitized. However, the lower 95% confidence limits for the increase in percentage parasitization of females compared to males were low (0.9-10.2%). The majority of adult simuliids carried only one parasite. The mean number of larvae per trapped parasitized host was significantly greater for 5. ortiattitn (2.69) than for S. eqtiinum (1.77). There was no significant difference between the mean number of parasites carried by the sexes of 5. ornattmi for each year from 1975 through 1978 but females were significantly more heavily parasitized than males during 1979. The ventral neck region of ali three host species is the main attachment site for Sperchon setiger larvae.The morphology ofthe pupae oiS. ornatum and 5. equinum is related to differences in levels of percentage parasitization between these two species. It is suggested that pupal morphology may be the most important factor in the selection of host simuliids by Sperchon setiger larvae.1)046-5070/82/0800-0345 $02.00

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This paper collects taxonomic changes in the families Hydrachnidae, Limnocharidae and Eylaidae which become necessary following revision of material from museum collections and recent field work. The following synonyms are established: Family Hydrachnidae, genus Hydrachna: The subgenera Anohydrachna Thor, 1916, Diplohydrachna Thor, 1916, Rhabdohydrachna K. Viets, 1931 are synonyms of Hydrachna s.str.; H. globosa neumani Lundblad, 1962a, and H. globosa rotundata Láska, 1964, are synonyms of H. globosa (De Geer, 1778); H. halberti Soar, 1908, H. levis Williamson, 1913 and H. levis acuminata K.O. Viets, 1954 are synonyms of H. incisa Halbert, 1903; H. perpera Koenike, 1908 is a synonym of H. processifera Koenike, 1903; H. skorikowi integra K. Viets, 1930 is a synonym of H. schneideri Koenike, 1895. Family Eylaidae, genus E ylais: E. bisinuosa nodipons K. Viets, 1919 is a synonym of E. bisinuosa Piersig, 1899; E. rimosa proceripalpis K. Viets, 1930 is a synonym of E. mutila Koenike, 1897; E. puripons K.Viets, 1930, E. bisinuosa oligotricha Lundblad, 1936, E. planipons novata K. Viets 1942 and E. canariensis Lundblad, 1962b are synonyms of E. planipons Walter, 1924. The following species must be regarded species incertae: Family Hydrachnidae, genus Hydrachna: H. aspratilis Koenike, 1897, H. bivirgulata Piersig, 1897a, H. brehmi Szalay, 1955, H. denudata Piersig, 1896, H. inermis Piersig, 1895, H. levigata Koenike, 1897, H. papilligera K. Viets, 1919, H. piersigi Koenike, 1897, H. regulifera Koenike, 1908, H. williamsoni Soar, 1908. Family Eylaidae, Eylais glubokensis Udalzov, 1907. The geographical origin of Hydrachna extorris Koenike, 1897, probably collected outside Europe, is unclear.

Following revision of material from museum collections and recent field work, new taxonomic and faunistic data are given for several representatives of the water mite superfamilies Hygrobatoidea and Arrenuroidea.