Larval habitats and life history of the Crete Island endemic Boyeria cretensis (Odonata: Aeshnidae)


Boyeria cretensis belongs to the most threatened European dragonfly species. It is restricted to some isolated permanent streams on the island of Crete. The streams have a pronounced gallery vegetation and are situated in a narrow belt of altitude between 50 and 400 m. We understand very little about the biology of this species so information is required to develop effective conservation measures. The life cycle and spatial distribution of the larvae were studied at a small perennial stream in the central part of Crete during three consecutive years. The larvae showed a preference for calcareous sinter mineral substrate associated with organic material such as roots, leaves and wood. This microhabitat selection is supposed to be mainly an antidrift strategy, since B. cretensis lives in habitats with a dynamic hydrology during the rainy period in winter. On the other hand, it may also be a strategy to avoid predation from fish and crabs. The last seven larval stadia were determined by wing sheath length and head width. Based on data of head width frequency distributions, a univoltine or semivoltine life cycle is discussed.

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