Ionic Regulation of the Hæmolymph in the Larvæ of the DragonflyIschnura Elegans(Vanderlinden) (Odonata; Zygoptera)

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Abstract
The larvae of I. elegans have been found to possess a highly developed ionic regulatory capacity. This was demonstrated by 2 types of experiments. In the 1st the change in internal ionic concentration was followed as a function of the time spent in a given experimental medium. The results obtained have led to a 2nd series of experiments in which the internal ionic concentration was compared to a series of increased concentrations of external media. A fixed external medium of 378 meq Cl and 352 meq Na leads to a constant internal medium of 342 meq Cl and 314 meq Na after a period of 120 hours. Increased concentrations of external media show that, both for Cl and Na, there is a marked regulatory capacity extending to the lower and higher sides of the external concentration in which the larvae are respectively hyper- and hypotonic.