Behaviour of the larval dragonfly Libellula depressa (Odonata Libellulidae) in drying pools

Numerous papers report that dragonfly larvae are able to survive dry periods in temperate areas. in this study, we investigated, in experimental field conditions in woodland, the behaviour of the larvae of Libellula depressa, belonging to the penultimate stadium (F-1), in a drying pond and the ability of these larvae to seek for water in dry conditions. Larval behaviour in a drying pond was studied using a small artificial pond that enabled water to flow out. Most of the larvae left the pond and, of these, a higher percentage left the pool after the formation of puddles. The ability of the dragonfly larvae to move towards a nearby pond was investigated by placing them 5 m away from a natural pond, with the freedom to walk on the ground. More of the larvae released nearest the low edge of the pond, where a humidity gradient was present, were able to reach water than of those released nearest the high edge, where no humidity gradient was present. The ecological significance of the behaviour of the larvae of L. depressa is discussed in relation to the typical habitat of this species, represented by small, shallow ponds, and to the presence of hygroreceptors in dragonfly larvae.