Monday, August 2, 2010

Backswimmers & Water Striders by Ralph H. Maestre BCE

Water Strider

Adults are between 5/16 to 5/8 inch long, dull to grayish or reddish brown above and silvery gray on the underside of the body. Many have long slender bodies with long, slender legs and antennae. The front legs are short and modified for grasping while the middle and hind legs are long, like stilts with claws. These insects creep on the surface of running water or pools in a slow deliberate gait where they feed on live and dead insects, crustacea and other organisms. They overwinter as adults. Long, cylindrical eggs are laid during spring and summer in parallel rows glued to objects at the water's edge. Adults are called "skaters" or "Jesus Bugs," apparently for their ability to walk on water of ponds, lakes and streams.

These insects are found in residential pools and will bite. The customer would have to shock (use chlorine) the pool. We do not treat for them.

Backswimmers - Notonectidae

Scientific Classification
Notonectidae or backswimmers is a family of insects of the Hemiptera order. Back swimmers, or Greater Water Boatmen are hemipteran bugs. They are named backswimmers because they are aquatic predators that swim upside down. They are up to 15 mm in size. They are similar to corixidae, but can be separated by differences in their dorsal-ventral coloration, front legs, and behavior. Their dorsum convex is light colored without cross striations. Their front tarsi are not scoop-shaped and hind legs fringed for swimming.

The size of air bubble that provide buoyancy changes as the nitrogen dissolve into the blood and the oxygen is used in respiration. Notonectidae carry extra oxygen supply using haemoglobin in their abdomen. This helps them regulate the size of its air bubble and the concentration of oxygen inside it. [1]

Backswimmer swimming on its back
The main genus of backswimmers is Notonecta- streamlined, deep-bodied bugs up to 16 mm long, green, brown or yellowish in colour. As the common name indicates, these aquatic insects swim on their backs, vigorously paddling with their long, hair-fringed hind legs.

Backswimmers are predators and attack prey as large as tadpoles and small fish, and can inflict a painful bite on human finger. They inhabit still freshwater, e.g. lakes, pools, marshes, and are sometimes found in garden ponds. They can fly well and so migrate easily to new habitats.

The Common Backswimmer is Notonecta glauca, widespread in the United Kingdom and Europe. Another species is N. maculata, distinguished by mottled brick-coloured forewings.

This is another insect found in residential pool and may bite clients. Again the homeowners must shock (use Chlorine). We do not treat for them.

a half-submerged Common Backswimmer (Notonecta glauca)

Chinery, M. (1986) Collins Guide to the Insects of Britain & Western Europe. Collins. ISBN 0 00 219137-7.
Fitter, R. & Manuel, R. (1986) Collins Field Guide to Freshwater Life. Collins. ISBN 0 00 219143-1.
Hungerford, H. B. (1933) The genus Notonecta of the world. U. Kansas Sci. Bull. 21: 5-195.

External links
Close-up photo by J. Hlasek
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