Are the attachment sites of larval water mites (Acari, Hydrachnidia) on their dipteran hosts suited for host partitioning?

Attachment site patterns for parasitic larvae of spring-dwelling water mites on nematocerans were recorded and evaluated. Emphasis is placed on mite larvae which parasitize chironomid hosts. Species-specific attachment sites on the hosts and site preferences in both thoracically and abdominally attached mite larvae were registered. A comparison between the attachment sites of single larvae and of two or more conspecific larvae parasitizing a single host revealed only small differences in attachment patterns, suggesting that site selection was the result of an innate preference rather than induced by competition. Balanced attachment was more frequent than asymmetrical attachment and dorsal/ventral attachment was found to be host-speciesspecific. Host partitioning was evident for those parasite-host associations in which one species parasitizes the host’s thorax and another parasitizes the host’s abdomen. Despite preferences for different attachment sites by the mite larvae, host partitioning was only rarely realized. This is because multiple parasitism was rare in the parasitehost relationships studied. We conclude that host partitioning caused by differences in attachment site preferences is likely for chironomid hosts but should be proven in a habitat with higher mite diversity, where competition would play a more important role.