
Ranatra linearis
Ranatra linearis
Water stick insect/Giant water scorpion (Ranatra linearis)
A member of the insect order Hemiptera and the family Nepidae found typically in weedy pools less than 1 m deep. World distribution unclear but has been recorded in the UK, in at least southwest and southeast England and South Wales. The only other British species in this family is Nepa cinerea, the smaller and better known water scorpion. Both are similar in that they have breathing tubes to draw air from the surface whilst submerged. However, whilst Nepa is flat and boat shaped, only superficially like a scorpion due to the breathing tube, Ranatra is reminiscent of a stick insect.
http://www.devonwildlifetrust.org/species/Water+stick+insect'2FGiant+water+scorpion/
http://naturdata.com/Ranatra-linearis-3866.htm

"Ranatra linearis" is a species of aquatic bug in the Nepidae family. They are typically five centimeters long. The breathing tube tail is often half the length of the insect. Their habitat is usually shallow water in weedy ponds. They are swimming insects, and the adults can fly.