Very recently, I discovered that there were small but visible creatures swimming in my pond, occasionally on the water surface, and sometimes in the water at depths of a few inches. These creatures measure about 4 mm to 6 mm in length, and when I took a macro picture of one in the water, I realised that it was the undersurface of a bug! The bug was swimming upside down!
This aroused my curiosity, and so I decided this afternoon, to fish one out of the water with a net to take a good look at the whole insect. Finally, after several photographs of it hopping on my terrazzo floor, I placed it back into the water.
Notonectidae is a cosmopolitan family of aquatic insects in the order Hemiptera, commonly called Backswimmers because they swim upside down. They use their long pair of legs like oars and paddle through the water at a good speed. They use their smaller legs to hold onto objects for protection from danger and to hold onto their prey.
The backswimmer water bug is found in shallow water abundant with aquatic plants and places to hide and a good supply of small prey. In Dug Pond they could be found around the perimeter in water up to 3 feet deep. They inhabit still freshwater, e.g. lakes, ponds, marshes, and are sometimes found in garden ponds. Although primarily aquatic, they can fly well and so can disperse easily to new habitats. They seem to be attracted to light; similar to a moth drawn to a flame.
You see them in the water, on their backs.
Showing mouth-parts, 1st and 2nd legs.
Backswimmers swim on their backs, vigorously paddling with their long, hair-fringed hind legs and attack prey as large as tadpoles and small fish. They can inflict a painful “bite” on a human being (actually, similar to a mosquito “bite”, it is a stab with their tubular mouthpart).The backswimmer’s life cycle consists of 3 stages, egg, larvae, adult. The larvae looks identical to the adult backswimmer but has a white color instead of green and brown. Also the eyes of the larvae are bright red instead of the brown/blue color of the adults.
In contrast to other aquatic insects that cling to submerged objects, Anisops deanei uses a unique system to stay submerged: using the extra oxygen supply from haemoglobin in their abdomen, instead of using oxygen dissolved in the water. The backswimmer feeds on small larvae and even bigger prey- like small fish. They feed by biting their prey and killing it with its venom and then eating it from the inside out with its unique tube-shaped mouth.
Backswimmer in the water.
Source: Information from Wikipedia and internet. Pictures are my own.