The visual communication of dragonflies

Biologists from the Conservation and Ecology Research Team Swansea (CERTS), working in collaboration with experts based in Milton Keynes, have investigated the visual communication of dragonflies – or Odonata

Their research paper, entitled Odonata colour: more than meets the eye? has recently been published in the International Journal of Odonatology (http://www.tandf.co.uk/journals/TIJO).  
The team, which includes Dr Wendy Harris, Dr Dan Forman and Professor Paul Brain from the Department of Biosciences, Milton Keynes-based Roy and Marie Battell, and Alan Nelson, the dragonfly county recorder for Buckinghamshire with the British Dragonfly Society, report many animals have a different visual range to humans and can see into the infra red and ultra violet spectrum, outside human limits of perception.  As such, it is sometimes easy for us to overlook this ability when considering the behaviour and communication of animals.
Dragonflies are efficient predators, both as nymphs and adults, and rely on their well-developed visual system to detect and capture their prey.  This sense is also used by territorial males to distinguish females, and identify rival males entering their territories.
The majority of species appear to possess UV sensitive pigments in their eyes that would enable them to detect this wavelength of light.  It had not, however, been determined how this capability is used by dragonflies or if the UV spectrum played any part in their colouration and communication. The team investigated the role of the UV signals in detecting rival males, as well as members of other species. A number of territorial British species were examined to determine the association of UV with visible wavelengths, and the differences in pattern between males and females, and between species.
Dr Wendy Harris, the paper’s lead author, said: “It was determined that UV signals are strongly associated with the blue colouration frequently observed on male dragonflies, and that a strong UV signal promotes territorial behaviour, even between species with very disparate colouration.
These signals are likely to play a significant part in advertising individual fitness, and may potentially aid in the camouflage of active males from avian predators.”