The Insect Diary: Native Cockroaches of Australia

A beautiful cockroach is quite an oxymoron. True in case of Australian bush cockroaches. They are not only visually stunning, but also most of them are not regarded as pests and are not associated with disease like their American counterparts. They mostly live in the bush and seldom get indoors. They feed on various insects and are the food of various small reptiles and other insects which makes them an important part of the ecosystem. Below are some native bush cockroaches of South West Western Australia.

Phylum: Arthropoda

Class: Insecta

Order: Dictyoptera

Family: Blattidae

1. Mitchell's Diurnal Cockroach

Polyzosteria mitchelli

Also known as Mardi Gras cockroach

This was found in Kalbarri National Park, Geraldton, Western Australia. It was basking in the sun on a leaf on a very windy day. This is an adult which is wingless and doesn't have any remnants of vestigial wings. It has dorso-ventrally flattened body which is characteristic of cockroaches. Its body is steal blue in colour with yellow markings on the thorax. It is quite a pretty looking cockroach.It is extremely shy and hide under the foliage when disturbed. They are known to emit pungent defensive fluid as self defence.

2.Ellipsidion Cockroach

Ellipsidion humerale

Ellipsidion is the most common and probably well known genus of Australian native cockroaches. They are winged and have beautiful golden lace like pattern on the wings. They are commonly found in woodland. They hide underneath the leaves and occasionally come up to sun themselves. They are very shy and rude away when disturbed. They are harmless, almost never live in houses and are not regarded as pests. Both the above photos are of Ellipsidion humerale.

3. Gisborne Cockroach

Drymaplaneta semivitta

Gisborne Cockroach: Drymaplaneta semivitta

Drymaplaneta sp. at the mercy of a Carnaby's Wall Skink (Cryptoblepharus australis)

The genera Drymaplaneta is native to Australia. The two species of cockroaches in this genera are commonly found both in woodlands and sometimes indoors. Even though they are found in large numbers sometimes, they do not infest food and not regarded as pests. The two species D. semivitta, the Gisbourne cockroach and D. communis, are very similar. The Gisborne Cockroach is uniformly dark and the hind tibia of the male are expanded compared to the Common Shining Cockroach (as seen in the above photo). Both have absent vestigial wings, unlike many cockroaches.

Below: photos of cockroach nymphs, mostly Ellipsidion sp.