Abstract
In the New Forest, Hampshire, England, two populations of Tipula luna Westhoff were studied on Alnus glutinosa Carr in the same strip of valley bog but separated by some 250 m. Using the multiple recapture technique of R.A. Fisher and E. B. Ford, the first population was shown to have been composed of 803 and the second population of 1797 individuals. Estimated interchange of individuals between the 2 popula-tions was 1.32%. Mean daily survival rates ranged from 66% (second population males) to 85% (second population females). Separate analysis showed that in second population males the highest daily survival rate occurred in the middle of the adult season. The sex ratio changed with time. Details of a population study on Tipula czizeki de Jong are also given.