During this time, inspection of infested banksia 
trees by torch light can reveal dozens of 
individuals clambering about. Males will savagely 
fight each other for access to females and it is not 
unusual to find males with antennae and legs 
snapped clean off by the razor sharp and 
powerful mandibles. During the day, these big 
beetles re enter emergence holes in the banksia 
trunks and wait for night fall. 
Females have a long ovipositerto probe cracks in 
the bark of host trees where they lay their hard, 
oval brownish coloured eggs. The larvae take a 
number of years to attain full size of 60-80 mm 
long. Before pupation, they chew out a large 
pupal chamber in the heart of the tree and line it 
with strips of wood. A tunnel wide enough to 
accommodate the future adult beetle terminates 
just in front of the bark. The emerging beetle has 
to chew through this to escape to the outside 
world, leaving the distinctive oval holes in the 
trunks of host trees. 
The second largest Tasmanian beetle is the 
Prionid Toxeutes arcuatus. This species is better 
known and perhaps more familiar to people as its 
large 50-70 mm, white larvae are often found 
while splitting decaying eucalypt fire wood. In 
general habits, this species is similar to P. australis 
however, it never infests living timber and its 
large oval emergence holes are commonly seen 
on large eucalypt logs and stumps, particularly in 
A large mature Banksia marginata stump riddled 
with P. australis emergence holes. 
wet sclerophyll forests. This species will attack a 
wide range of timbers including large dead radiata 
pines. These beetles can attain 50 mm in length 
and all the largest specimens I have seen have 
been females. They also emerge in enormous 
numbers on hot nights in late summer. 
Some large eucalypt logs can give rise to 
hundreds of beetles. This species can be easily 
found at the right time of year simply by lifting 
sheets of loose bark on living eucalypts where 
they shelter during the day. They are also strongly 
attracted to electric lights. 
The best way to differentiate between the two big 
Prionids is to examine the edges of the thorax. In 
P. Australis, the thorax is fringed with lots of 
small, tooth-like spikes. In T. arcuatus the thorax 
has four large, curved, very sharp projections, two 
at the top and bottom of each side of the thorax. 
T. arcuatus is also more dorso-laterally flattened 
(for getting under bark) and has a gloss finish 
rather than the matt finish on P. australis. 
The third largest beetle in Tasmania is entirely 
different. The 40-45 mm Hydrophilus latipalpus is 
our largest water beetle. This species is a 
vegetarian and lives in lagoons, marshes and 
dams. Although common and widespread, it is 
rarely seen by the casual observer due to its 
Larval bores and pupation chambers of P. australis 
in a large Banksia marginata 
Tasmanian Field Naturalists Club BULLETIN 341 January 2011 p8 
