Pied Percher (Neurothemis tullia) is a small-sized dragonfly with a body length of about three to four centimetres commonly found in Hong Kong. It inhabits wetlands like paddy fields and marshes. It has a very short hatching period and adjustable larval development which can be hurried when water levels of mercurial wetland habitats are low. The adults move homes if the environment becomes unfavourable. The adaptability of the little dragonfly is an example of survival of the fittest of the natural world.
Pied Percher is a species of dragonfly in the Family Libellulidae. Its wings have a prominent black and white pattern with over half of the wing surface coated in dark brown to black from the wing base bordered by a white splash which fades to hyaline on wing tips. The recognisable pattern makes it very eye-catching, particularly the male. Females have duller black and white colours. The black and white pattern provides Pied Percher a camouflage in the light and shields it from predators' detection when it perches among grasses or dried stems.
Pied Percher has light and slow flight movements, unlike the fast and direct flight of larger dragonflies. It flies as gracefully as a butterfly in an erratic course. Such flight mode helps it navigate in labyrinthine shrub thickets and avoid being tagged on the bull's eye by predators.
Hong Kong's Pied Percher occurs on the wing from April till October and is most active in the golden hours of dawn and dusk. It prefers still or slow-moving waters and frequents places like paddy fields, marshes and edges of ponds with lush vegetation. Its disregard of water quality and strong adaptability allow it to be widespread in Hong Kong.
Versatility
Pied Percher has developed a set of versatile survival strategies to keep it thriving in dynamic wetland ecosystem like paddy fields which have unstable water levels. In 1990s, a Malaysian scholar noticed it had a very short life cycle manifested in brief hatching and larval stages in his study of life history of rice field Pied Percher. It spends about eight days hatching and seven to twelve weeks as a larva in its life cycle. These adaptations enable the reproduction of four generations of Pied Percher in a year. Its eggs are drought resistant and hatch immediately as soon as it rains after a dry spell.
The larval stage of Pied Percher is variable. Larval growth is uniform during early instars. Variations in larval size occur in later instars when competition or the environment worsens. Larvae omit some instars in order to emerge early. Most surprisingly, emergence of the adults is synchronous regardless of differential larval growth. This has ensured proliferation of the species when the condition is right.
When there is a drought, the adults resettle to nearby grasses or forests for temporary refuge and return when the wetland ecosystem revives. Pied Percher's traits of fast growing, multivoltinism and swift relocation have allowed it to thrive in the fluid environment of wetlands.
