Water striders

Water striders
  • They are small insects that are adapted for life on top of still water.
  • By using surface tension to their advantage, they can walk on water.
    • Water acts different at the surface.
    • Water molecules are attracted to each other and like to stay together, especially on the surface where there is only air above.
    • The attraction between water molecules creates tension and a very delicate membrane.
  • Water striders walk on this membrane.

Physical features
  • They are about a half-inch long with a thin body and three sets of legs.
  • They have three pairs of legs.
  • The legs have tiny hairs that repel water and capture air.
  • By repelling water, the tiny water striders stand on the water’s surface and the captured airs allows them to float and move easily.
  • The striders possess needle-like mouth parts that are used for sucking the juice of prey.
  • There front legs are relatively shorter than the mid and hind legs and used to catch and hold prey.
  • They eat insects and larvae on the surface of water, such as mosquitoes and fallen dragonflies.
  • Water striders act as a water quality indicator as they are found on water surface.
  • They play an important role in the food chain by feeding on mosquito larvae.
Subgenus Ptilomera
  • Water striders have many subgenus, one of them is Ptilomera.
  • They are only found in rocky, fast flowing streams and rivers that are not exposed to a lot of sunlight.
  • They  have hair on the middle legs that help the insects resist the strong current of streams.
Ptilomera nagalanda Jehamalar and Chandra
  • It was found in the river Intanki of Peren district.
  • It has orange with black stripes on the dorsal side and a pale yellowish brown ventral part of the body.
  • The presence of black stripes on the dorsal side differentiates this species from other known species of the subgenus Ptilomera.
  • It has long slender legs and measures about 11.79 mm.
Water striders of subgenus Ptilomera found in India
  • So far, only five species of water striders under the subgenus  Ptilomera were known in India. These include:
    1. Ptilomeraagriodes: It is found in peninsular India
    2. Ptilomeraassamensis: It is found in northeastern India
    3. Ptilomeralaticaudata : It is found in northern and northeastern India
    4. Pltilomeraoccidentalis : It is found in Uttarakhand.
    5. Ptilomeratigrina : It is found in the Andaman islands.
  • With the discovery of Ptilomera nagalanda, the number of species of water striders belonging to the subgenus has increased to six.
Section : Environment & Ecology