Visual and tactile stimuli in choice of oviposition substrates by the dragonfly Perithemis mooma Kirby (Anisoptera: Libellulidae)

Prior to the establishment of a territory, males select a suitable oviposition substrate which is detected by visual and tactile stimuli. Video films analysed in slow motion revealed that the individuals extend their hind legs while making short dips over the oviposition substrate, touching the ground for 0.01 – 0.02 s with the tarsi. Females use their legs in the same manner during oviposition. By setting up experimental oviposition sites it could be shown that the individuals are first guided by their visual and then by their tactile sensory system. Pancake-like substrates consisting of fine structured, emergent material completely surrounded by water are accepted visually and arc subsequently examined physically with the tarsi. Choice experiments with various materials revealed that only those substrates which have a gelatinous surface are accepted. Following site selection the males perch nearby, perform patrolling flights and chase conspeciftc intruders, while the females oviposit at such localities.