Padded Diving Beetle
Male: Pad, profile
Ellura
Padded Diving Beetle
Male: Legs, ventral
 
    
Padded Diving Beetle (Eretes australis)Class: Animals (Animalia) - Jointed Legs (Arthropoda) - Insects (Insecta)
Order: Beetles (Coleoptera)
Family: Diving Beetle (Dytiscidae)
Species: Padded Diving Beetle (Eretes australis)
This Photo:     Male: Pads, ventral

General Species Information:
Found on Ellura (in the Murray Mallee, SA) and elsewhere
After the heaviest rainfall since June 2019, we found a large number of these in early Feb 2020.
We found 3 dead specimens in the past (Mar, Jul & Aug).
The males have padded feet, shown here, used to hold onto the female when mating.
The female we measured was slightly smaller than the male, with the female being ~13mm & the male being ~15mm. There did seem to be a lot of size variation in specimens we saw.
They can fly, and breath air, taking a bubble of air with them when diving to the bottom of a water source.
They are very fast swimmers. They have hair on their middle & hind legs that act link fins. When out of the water these hairs collapse into a row along the edge of each leg.
The patterning on their elytra seems to vary quite a bit, but there always seem to be a solid black mark about midway down the elytra, along with 2 or 3 rows of small black marks (mixed in with light & dark patches) that aren't very obvious in the live specimens.
Compared to other diving beetles, the head does seem more prominant/protrudes from the body. Pronotum shape is also useful to help with diagnostics. The male feet seem unusual, but are similar to some other diving beetles.
The Pictorial Guide to the Diving Beetles of SA says "A distinctive species, unusual in having the surface punctuation on the prothorax much smaller than on the wing cases.", which is quite obvious here.

Copyright © 2020 Brett & Marie Smith. All Rights Reserved. Photographed 01-Feb-2020
This species is an Australian Native Species, not listed in the SA Murray Mallee Survey of 2010.