Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Subclass: Pterygota
Order: Coleoptera
Suborder: Adephaga
Family: Dytiscidae
Genus: Rhantus
Species: R. suturalis
Scientific name: Rhantus suturalis
Common name: Predatory diving beetle 

Rhantus suturalis is a diving beetle (length > 12.5 mm) that is common throughout New Zealand and it is also found overseas. 
It lives in still water habitats such as ponds, water troughs and the edges of lakes and pools that dry out in summer. These habitats are also the breeding places of mosquito larvae, which are the preferred food of this beetle. They can fly very well, and so easily escape from a pool which is drying out and migrate to another.
They trap air beneath their wings allowing them to breathe as they hunt under water. They swim using their large hind legs and paddle-like feet. The beetle has a light yellow coloured margin and a rhombus-shaped dot on the neck shield.

Predatory Diving Beetle Rhantus suturalis 18-05-2016 10-29-14 AM. subpauperatus-003.jpg 

Predatory Diving Beetle Rhantus suturalis 18-05-2016 10-29-32 AM. subpauperatus-004.jpg

Predatory Diving Beetle Rhantus suturalis 18-05-2016 10-29-49 AM. subpauperatus-005.jpg 

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