1. The influence of seasonal flooding on wetland insects is understudied, and understanding of a potentially important influence on population dynamics is therefore incomplete. This is of particular consequence because many wetland insect species, including the large copper butterfly, Lycaena dispar batavus, are of conservation interest.

2. Previous studies on the submergence tolerance of diapausing L. d. batavus larvae have been inconclusive. This study investigated the effects of different periods of enforced submergence on overwintering survival, using both fresh and brackish water, and comparing effects on larvae in early and late diapause.

3. Larvae were submerged for up to 84 days, and survival was negatively correlated with submergence period, although periods of up to 28 days did not appear to reduce survival. Water type, i.e. fresh vs. brackish water, and larval stage, i.e. early vs. late diapause, had no significant influence on survival.

4. The relevance of these findings to the population biology and conservation of L. d. batavus is discussed. Further studies on the effects of submergence by seasonal flooding on wetland insect populations are encouraged.