Observations on ventilatory and net‐spinning activities of larvae of the genus <i>Hydropsyche Pictet</i> (Trichoptera, Hydropsychidae) under experimental conditions

Abstract

Summary Larvae of three species of the genus Hydropsyche with distribution patterns indicating they are associated with increasing ranges of flow rate and temperature in the sequence H. instahilis, H. pelhicidula, H. angustipennis, were selected for study. Experiments on frequency of ventilatory movements indicated that the larvae were increasingly tolerant to dissolved oxygen concentration, flow rate and temperature in the same sequence of species. Experiments on net‐spinning indicated a corresponding order of preference for higher temperatures and a general preference for higher flow rates. During experiments on net‐spinning the number of larval casualties, ascribed to encounters between individuals, showed marked contrasts between species. The significance ofthe behaviour ofthe larvae under experimental conditions is discussed with reference to their distribution in the field.