This is a very distinctive bug being round with a long rostrum, juveniles are just a smaller version too. It is found in moderately fast rivers and streams with stony or gravelly bottoms, interstitial silt and a little vegetation where it swims rapidly, or walks slowly along the bottom. The River Nene, its tributaries and the River Tove have this habitat occasionally.

It never leaves the water and has a well developed respiratory mechanism. It is largely covered by microscopic hairs which are un-wettable by water (at pressures likely to be encountered at all but great depths) and gives maximum water-to-air surface. The air-filled pile is contiguous with the ventral spiracles: however, were the spiracles of normal form they would either collapse under the water pressure or become waterlogged. Instead, the spiracular openings are expanded to form a flat bag or external gill (SWL, 1959).

The bugs mostly overwinter as adults and mate and oviposit in late spring and through the summer. Eggs are fixed singly to stones and sometimes to old mollusc shells. The diet is strictly carnivorous, mainly of chironomid and mayfly larvae.

Distribution:

This is widespread across Northants and will be found wherever the habitat is favourable. However has currently only been recorded from the faster flowing areas of the River Tove and River Nene and therefore scarce in Northants.

Habitat:

Found in moderately fast flowing water mainly over gravel with overhanging vegetation, however can be in fast flowing silt bottom streams too. It is very sensitive to pollution and can easily be eliminated from a river system if polluted.

Identification:

This is an easily identifiable round, matt brown bug between 8 and 10mm with a long rostrum.