Water boatmen (Family Corixidae)

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Suborder: Heteroptera
Infraorder: Nepomorpha
Family: Corixidae
Common name: Water boatmen, 

The aquatic insects in the family Corixidae are unusual among the aquatic Hemiptera in that they are mostly non-predatory, feeding on aquatic plants and algae instead of insects and vertebrates. There are over 500 species of water boatmen in the world.
Water boatmen are common, inhabitants of slow-flowing streams, lakes, ponds and troughs, feeding on algae and organic detritus. They swim belly down using their long hair-fringed hind legs. They use a scoop at the end of their forelegs to move food towards their soft tube-shaped mouthparts. Enzymes are then injected into the plant. The enzymes digest the plant material liquefying it enabling the insect to suck the liquefied food into its digestive tract.

The adult bug can fly and hence it is able to populate other habitats. Eggs are attached to underwater plants and rocks. The hatch nymph will moult several times before becoming an adult. Wings are formed during the last moult. Lifespan is about a year.

To breathe underwater a water boatman carries an air bubble under its shell. This makes it slightly buoyant and so to stop floating back to the surface it hooks its legs onto plants or rocks.

This photo is a young of the Sigara species.
Water boatmen 2.jpg 

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/