Have a look at this one; it would have to be amongst the most colourful of any insect. Its name is Polyzosteria mitchelli, but is generally known (along with many other species) as a Bush Cockroach from the family Blattidae. It grows to around 5 cm in length.
Bush Cockroach, Polyzosteria mitchelli
This Platyzosteria species is seldom more than 3 cm in length and can be found at night, quite high in trees where it seeks out flowers on which it feeds. It is also found on the ground and probably is a common prey species for mammals, frogs, reptiles, arachnids and night birds. In defence, many species including this one, will raise up their rear and release a foul smelling concoction to deter any predator with a sensitive nose.
Being completely black, it can play the part of Darth Vader very convincingly.
A Cockroaches life however is not all fun and games, as they have parasites that can be fatal, one of these is the Gordian worm belonging to phylum, Nematomorpha. The adult worms intend leaving their host near water so they can breed and provide habitat for their aquatic young. However, as can be seen with this one, the host is not always cooperative and the worm also dies. (My thanks to the Australian Museum for this information)
This next species (also from the family Blattidae) can easily be confused with the black variety above (similar looking cockroach species can only be distinguished by their genitalia). However, this species was reasonable distinctive, being a dark bronze in colour, slightly smaller, with shorter leg spines and a pale horseshoe shaped area along the upper shield edge.
This pair are intent on making a large ootheca full of viable eggs. Note the small one (probably the male) compared to the much larger female. Dimorphism and other differences are not unusual with cockroaches and some males and females have in the past been described as different species.
This lady having made her ootheca, is looking for a good spot to place it. Note how fat these animals are, quite unlike the introduced cockroaches, which tend to be flat with both sexes winged.
Yet another cockroach from the Blattidae (this family by the way, is the largest of the five Australian cockroach families, having as many species as the other four families put together). This one is a Drymaplaneta species, or a Bark Cockroach and has a prominent creamy/white horseshoe marking on the shield.
Although having no wings, it is a very good climber (here on glass).
This is a juvenile Blattodea species typically feeding from a Banksia speciosa flower.
Now for a different family! It includes the largest (to 7 cm) and most bulky cockroach in the world and lives here in north Queensland, it is a member of the Blaberidae family. However, this Esperance WA species is much smaller, being less than half that size, but it has the characteristic broad, bulky shape and short legs. These are social animals and raise their young in underground chambers, or under leaf litter, in rotten logs, or dead Grasstrees (Xanthorrhoea sp.) and because of their shape, are commonly known as Trilobite Roaches. The males of these Calolampra species are usually winged, yet they all live together in communities with the females and the young, apparently communicating with each other by scent.
This group with the large, more heavily armoured outer shield, which combined with shorter legs (ideal for digging) are a much slower moving cockroach than most people are familiar with. They probably move around less too, so are not commonly seen unless you happen to be near their nest.
And who could resist this shy modest Trilobite Roach?