This is known as the River Skater and occurs at the margins of lakes and on rivers and large streams requiring flowing water. It is widely distributed across the UK with the Western and Southern bigger and faster flowing rivers its heartland. They are a large surface bug between 13mm and 17mm and can form large surface colonies.

Overwintered bugs mate in May, but mating records for other months complicate the picture as the male and female and ride atop of each other for a long period. Evidence suggests a single breeding period with presence all year but a peak during July, August and September. (NBN 2019). They are oriented up stream towards rippling sensations of flow or wave wash by long sense hairs on their hind legs. These also help to detect struggling insects which they prey on. They can feed on aquatic inverts but also on insects blown onto the surface.

Habitat and Distribution :

There are not too many habitats that would suite this in Northants as the River Nene is perhaps a little slow flowing, the River Welland skirts the northern Northants border and the Ouse skirts the Southern boarder. It has not been found on the River Nene despite searching however it is also not present on the Welland and Ouse in bordering counties to my knowledge but this is perhaps more lack of recorder effort. This was found once on the River Welland at Duddington where it just comes inside the Northants border.

Identification:

As large bugs on the water surface they are easily identifiable to within a few species. They are dark coloured and the spines on either side of the last abdominal segment don't reach the tip of the abdomen. This can easily be differentiated from Aquarius paludum which has a yellow stripe on the side of the thorax and the spines on the last abdominal segment form a 30 degree angle and are the same same length or longer than the tip of the abdomen