Great diving beetles
27th April 2008, SundayFive of the six species of great diving beetle Dytiscus species have been recorded in the RX area, and the adults and larvae of these impressive carnivorous beetles can currently be observed cruising around our ponds and ditches. The largest and rarest species, Dytiscus dimidiatus, a Red Data Book species, has been recorded growing up to 39mm and is an impressive insect. I have found it in a number of ponds at Dungeness, and in ditches on East Guldeford Level, and The Dowells, and others have found it at New Romney. This specimen, a male, was taken in a trap last week in a pond that was 70% shaded.
Although Dytiscus species are superficially similar, large beetles, shiny black above with creamy edges to the body, they are sufficiently distinct to be told apart with some ease. Apart from its large size, Dytiscus dimidiatus can be identified from the cream markings around the edge of the elytra. These do not cut across the thorax, or more correctly the pronotum, in water-beetle speak. Only two British species look like this, the other being the more common Dytiscus semisulcatus, but this species is black underneath, whereas the ventral surface of dimidiatus is a creamy-brown colour.
The larvae are more difficult to tell apart, and are fierce creatures, devouring tadpoles in large numbers, and if over-crowded, each other!
