Site selection and growth of the larvae of Eylais discreta Koenike, 1897 (Acari, Hydrachnellae)

The distribution of the larvae of Eylais discreta on the abdominal tergites of the host species Sigara striata, S. falleni and Cymatia coleoptrata is examined. On S. striata and S. falleni the segments 3 and 4, on C. coleoptrata the segments 2 and 3 are successively preferred. There is but little influence of multiple infestations on this distribution. The growth rate on the various tergites of S. striata is similar, while on C. coleoptrata a possible difference could not be proved statistically. The larvae of E. discreta generally hibernate on the host; during this phase there is little growth; not until March-April they start growing faster. The larvae on C. coleoptrata are retarded in growth compared to those on S. striata. The larvae on S. falleni do not show any increase in size; this water bug species is immune to infestation by various Hydrachnellae.