ALTERATION OF HOST STAGE DISTRIBUTION BY PARASITIC WATER MITES OF THESPECIES HYDRACHNA-VIRELLA (ACARI, HYDRACHNIDAE)

The effect of a parasitic water mite, Hydrachna virella, on the stage distribution (the proportion of the host population represented by a s tage) of its aquatic insect host, Buenoa scimitra, was studied using a stage-based matrix model. Despite killing members of several stages, the mite increased the stage-distribution values of those stages. This effect seems to result from a lag in the rate of development of paras itized hosts; parasitized hosts remain in a stage longer. Consequently , a stage with parasitized individuals would represent a larger propor tion of the host population than would the same stage with only unpara sitized individuals. Parasites that delay host development can bias fi eld estimates of prevalence or proportion of a host population (or sta ge) parasitized.