Euzosteria tuberculata - Common Tortoise Cockroach

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Euzosteria tuberculata - Common Tortoise Cockroach 

In the Esperance region, this cockroach is an inland species, although it extends to the coast across the Nullarbor and the SA York Peninsula, but otherwise mostly covers the drier portion of central and northern Australia. 

I encountered a small colony on the outer apron of a large rocky outcrop called Mt. Newmont in the mallee 150 km (93 miles) NE of Esperance, which locally would be on the southern edge of its distribution. A large bushfire had passed this outcrop a year or two before, but due to the extensive rocky platforms, small areas had not been burnt and it was in these I encountered this roach. They were feeding on a tall dead Baeckea species (not burnt) that is common around these granite outcrops, but were not seen feeding from any that had been burnt. 

 This species is apparently unique in its colour pattern and series of ridges on the thorax, plus the number of tubercles over most of the upper body that would I think give rise to its species name of E. tuberculata. It is a handsome cockroach growing to 25 - 29mm (little over 1”) in length. 

 Euzosteria is part of the Blattidae family. 

Reference: 

A Guide to the Cockroaches of Australia 

By David Rentz. 2014.

Drymaplaneta variegata - Flat-footed Wood Runner

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Drymaplaneta variegata - Flat-footed Wood Runner

Drymaplaneta variegata belongs to the Blattidae family, which is the largest of the Australian cockroach families and contains many of the colourful wingless bush cockroaches, as well as a couple of introduced pest species (American and Asian) that have wings and like to cohabit with people. Most Australian species are quite harmless having clean eating habits (so not disease carriers) and rarely enter houses, although a similar looking cockroach Drymaplaneta communis (restricted to the Eastern States), has apparently become very numerous around Sydney and Melbourne and although it might enter houses is quite harmless.

The Drymaplaneta genus and most of its species have previously been placed in the Cutilia and Methana genera, and of the six Australian Drymaplaneta species (Australian Faunal Directory), five are recorded for the SW of Western Australia, so all could be in the Esperance region. Drymaplaneta variegata (25-34 mm in head/body length), is very similar to another local Drymaplaneta semivitta, but that species is less than half the size of D. variegata.

The Drymaplaneta species above is not particularly common around Esperance, although odd ones come and go. Their preferred habitat is under loose bark, which is not overly abundant in heathland and may reflect its local absence, but they could be more common in low-lying areas where there are more eucalypts, but being wingless, a hundred metres/yards can be quite a walk if you are only 3 cm (little over 1”) in length.

Reference:
A Guide to the Cockroaches of Australia
By David Rentz  2014 

Zonioploca medialinea - Midline Desert Cockroach

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Zonioploca medialinea - Midline Desert Cockroach

This is another mallee cockroach that was found near Mt Buraminya 130 km (80 miles) NE of Esperance, where encountered under eucalypt litter in a fine sand/clay soil over limestone.  I had stopped for lunch and whilst doing so, this guy appeared, so not sure if it is more active during the day or at night, it was however quite fast, dashing from cover to cover.

The cockroach was around 2 cm (nearly 1”) in head/body length and as only one was seen, I was unable to ascertain other details or if it was locally common.  The area has a good tree cover, with small Melaleuca and other shrubby species making up the lower story; median rainfall is around 40 cm (16”) per annum, with hot dry summers.

Reference:
A Guide to the Cockroaches of Australia
by David Rentz  2014

Bronze Cockroach - Euzosteria nobilis

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Bronze Cockroach - Euzosteria nobilis

Euzosteria nobilis  is a member of Blattidae, the largest cockroach family with over 200 Australian species, which are generally known as Bush Cockroaches.  The genus Euzosteria has 10 species (Australian Faunal Directory).  I have called this species ‘Bronze Cockroach’ as it clearly defines the one around Esperance, which is otherwise very similar to the Black Cockroach (see right hand column for details).  However there are a number of bronze coloured cockroaches around Australia, with this species also occurring in SA and Victoria.

Care must be taken when viewing Euzosteria nobilis at night as some individuals are very dark and you must direct the light in the right direction to distinguish it from the more common local Black Cockroach, which is much the same size, around 3-4 cm (11/2”) in length.  In the heathland around Esperance the Bronze Cockroach would be the second most common species (after the Black) and is often encountered.

Copulating cockroaches are rarely seen locally, so the couple above was an excellent sighting.  The timing of this event was August, probably permitting the young to hatch before the onslaught of a hot/dry summer, when this species in particular becomes very scarce. Euzosteria nobilis are very bush orientated and do not invade houses, not even accidentally, although they can sometimes be found wandering around outside where they feed on slowly (not mushy) decaying vegetation.

My sincere thanks to James  Walker of North Queensland who kindly identified this species.

Blue-rump Cockroach - Melanozosteria sp.

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Blue-rump Cockroach - Melanozosteria sp. 

The Melanozosteria genus is according to Dr D Rentz (Australian Blattodea Authority) a large difficult group to identify; containing many undescribed species in the Blattidae family, which are often darkly coloured with limited markings. You would think the blue rump would be a distinguishing feature, but this is not necessarily the case, as the color is formed by an opaque mucous-like adhesive substance, overlying the dark blue/black exoskeleton and changing it to a lighter blue, so other species may be similarly coloured. I have called this roach by this common name purely to more clearly separate it from the many other unidentified species shown in this blog. 

The opaque mucous-like adhesive substance (not present in all species) was brought to my attention by David Rentz, who remarked that he had seen a spider attack a cockroach with this rear-end coating, only to have it quickly retreat with gummed up mouth parts, thereby indicating an effective defence mechanism. In the paper by Oliver Betz and Gregor Ko¨lsch called ‘The role of adhesion in prey capture and predator defence in arthropods’  they state “Among the diverse epidermal glands of cockroaches, there are at least two sets that produce a defensive secretion……. The gland tissues are located dorsally in abdominal segments…. and on the cerci. Predators are mechanically impeded by the viscous secretion, which forms long threads that usually break on the side of the cockroach and stick to the predator…….. The secretion consists of 90% proteins (dry mass) and is not toxic…..” The on-line paper available here.

The mature cockroach above with the blue rump was around 2 cm (3/4”) in head/body length, whilst the juvenile brown ones were about 25% smaller. I encountered these insects in mallee heath, 140 km NW of Esperance in a shallow sandy loam over gravel. Similar looking juveniles were seen in broken granite at the base of a large rocky outcrop 140 km NE of Esperance, which is 230 km (140 miles) due east of the above sighting. So possibly the Blue-rump Cockroach is a common inland species of gravel/rocky habitats.

Zebra Cockroach - Robshelfordia hartmani

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Zebra Cockroach - Robshelfordia hartmani 

The endemic Robshelfordia cockroach genus currently has 12 species and belongs to the Blattellidae family. It is thought that this species Robshelfordia hartmani, is associated with termites as they have been found in rotting, termite ridden logs, although a specimen has also been found in a cave. 

Robshelfordia hartmani is currently only known from the SW coastal region of Western Australia, with the above encountered wandering around in sandy Banksia heath, 20 km (12 miles) east of Esperance. I asked Dr D Rentz who kindly identified this species, if they were common to which he responded “it is not known if it is common. Who collects cockroaches!” This I think sums up the position of most of our indigenous roaches, specifically they are very poorly known. 

Males of this species are fully winged, but the wings of females are much reduced (as the above). However this situation does not apply to all Robshelfordia spp. for with at least one species both male and female are fully winged. 

The individual above was around 1 cm (3/8”) in head/body length and is the only one of this species I have seen over a number of years looking for unusual invertebrates, so locally they are far from being common. The name Zebra Cockroach is my own invention to better aid the recall of Esperance species, especially those people like me with a poor memory for Latin and Greek.

Winged Cockroach - Balta sp.

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Winged Cockroach - Balta sp.

The Balta genus belongs to the Blattellidae family that has many winged species, including the introduced house invading ‘German Cockroach’ pest, which is probably an Asian species. The Blattellidae family is most obviously distinguished from other cockroach families by having antennae longer than half the body length, long sender spiny legs, plus reasonably long tapering cerci that are carried at right angles to the body.  Other features involve the genitalia that can only on be seen on the underside. 

Most of the Australian Balta cockroaches are endemic and unlike the German Cockroach seldom enter houses, although sometimes they are attracted to house lights. In the Esperance region although these roaches are widespread, they are not particularly common and seldom encountered. Balta are generally small insects with the above being around a cm (3/8”) in head/body length and spend most of their time wandering around on native vegetation.

Only the Balta males are winged, whilst the females have much reduced ones and cannot fly. Like many female wingless insects, they probably release pheromones to attract the similar sized male when ready for mating. Locally, they are most often seen on calm warm evenings, particularly after light rain.

Anamesia polyzona - Impostor Sleepy Cockroach

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Impostor Sleepy Cockroach - Anamesia polyzona

The Anamesia genus with 11 species (Australian Faunal Directory) is a member of the Blattidae family and the Polyzosteriinae subfamily, which are well represented in the Esperance district. This particular species was encountered in the Mt Buraminya mallee region (140 km or 85 miles) NE of Esperance, when I stopped for lunch under a clump of eucalypts on the edge of an open plain. These plains are created by a shallow fine sand/clay over a very hard limestone, thereby restricting root penetration and development of trees and large shrubs.

Anamesia polyzona is between 2-3 cm (1”) in head/body length and recorded as being diurnal (active during the day). And besides ducking for cover under eucalypt debris, they are also known to hide under sand and to sunbathe. The one photographed above was active at the end of August, when days are pleasantly warm and sunny, but nights chilly (around zero degrees Centigrade).

The common name of  "Impostor Sleepy Cockroach" is due to its similarity with species in the Cosmozosteria genus.

Reference:
A Guide to the Cockroaches of Australia
by David Rentz  201

Drymaplaneta heydeniana - Golden Cockroach

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Golden Cockroach - Drymaplaneta heydeniana

This species has also been known as Cutilia heydeniana (amongst others) and is another member of the Blattidae family. Locally in sandy Banksia heath, it does not seem to be common unless not attracted to house lights, whatever the case I have rarely encountered it.

To quickly separate it from other local species, I have called it the Golden Cockroach, but the pale margin extending the full length down either side and boarded by a thin dark band are distinctive features. The photographed female was over 2 cm (almost 1”) in head/body length and appeared at night during early February, so Drymaplaneta heydeniana is apparently still active during the hotter time of the year.

For additional details about Blattidae cockroaches, please refer to ‘Insects – Cockroaches’ in the right-hand column.


Update December 2010
Two photographs added

Platyzosteria sp. - Tattooed Cockroach

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Tattooed Cockroach - Platyzosteria sp.

The Tattooed Cockroach is a most unusual species and differs remarkably from others in the Esperance region. It is quite small being a little over 1 cm (1/2”) in head/body length and you would not be amiss to consider it a juvenile of one of the larger species, but the sighting of the odd shaped ootheca (egg case) would soon dispel that notion. The shape of the ootheca above is not restricted to the photographed individual, as I have a photo of another female with an identical one.

However, it is the tattoo-like markings on the back that are quite extraordinary and which are repeated on all individuals encountered. How such an elaborate patten could originate and for what reason is somewhat baffling, particularly when so artistically produced. I find it another little wonder that makes nature observation so rewarding.

This little gem of a cockroach, apart being found on the ground, is often encountered at night, feeding on fresh Banksia blooms at some height. The Tattooed Cockroach is not especially common in the Esperance Banksia heathland, but is regularly seen during the cooler months, although being small it would easily be overlooked in less contrasting habitats.

Platyzosteria sp. - Orange-rump Cockroach

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Orange-rump Cockroach - Platyzosteria sp.

I have called this member of the Blattidae family the Orange-rump Cockroach, simply to distinguish it from other Platyzosteria species that I am unable to identify. It is also possible that it is an undescribed species, which with invertebrates, especially in the remoter parts of the Esperance region is quite feasible.

This attractive cockroach was encountered at night in mallee habitat (fine sand/clay over limestone) on the edge of an old gravel quarry (used for road construction), 100 km (62 miles) NW of Esperance, off the Neds Corner Road Extension. It was a little over 2 cm (1”) in head/body length and had just emerged from its shelter in a near horizontal hole on a steep slope.

If anyone can identify this and other cockroach species, or has photographs of a similar looking one, would you please email me at wa@wn.com.au so the details can be added for future reference.

Calolampra fraserensis - Trilobite Cockroach

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Trilobite Cockroach - Calolampra fraserensis

The genus Calolampra is one of 15 in the Blaberidae family, which according to the Australian Faunal Directory has a total of 87 species. However only three are listed for the southern coastal district of Western Australia, with the vast majority found in the Eastern States, particularly in Queensland and northern NSW. This family of roaches are generally flat and have shorter legs than those in other families and due to their segments and rounded shape are commonly known as Trilobites after a similar looking marine arthropod that went extinct 250 million years ago.

Some cockroaches in the Blaberidae family are amongst the largest, or at least the heaviest and live in burrows underground. Calolampra fraserensis also lives in the soil or under litter, but do not construct complex tunnels, although livable spaces are made where they will cohabit with other family members.

Despite some Blaberidae being completely wingless, the males of most species do have wings (females remaining wingless), to no doubt enable them to migrate to other colonies thereby spreading their genes and so reducing the risk of inbreeding. Mature insects of the above species are a little over 2 cm (3/4”) in head/body length and although I would not class them as being common, are still well represented in the Esperance region, but are seldom encountered, presumably remaining close to home.

Platyzosteria sp. - Black Cockroach

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Black Cockroach - Platyzosteria sp.

Although this Black Cockroach has long been a member of the Blattidae family, the same thing cannot be said for its genus, as some species have been moved around 5 or more times. Mostly they have retained their species name, but with this one known as Cutilia nitida 100 years ago, have in more recent years disappeared off the radar and despite extensive searches I have been unable to find it again. It seems you need to be very well acquainted with cockroach taxonomy to appreciate what has been happening with them.

However, the Black Cockroach around Esperance is very common, particularly in sandy heath. They only come out at night and although far from being in plague proportions, are often the only invertebrate encountered. Nevertheless, they are an important food source for many animals, particularly frogs, which in turn provide sustenance for other predators like reptiles, so locally these cockroaches are a key feature in the heathland ecosystem.

Occasionally they do enter houses, but are not dirty or become a pest; they just go about their business feeding on dry, slowly decaying organic matter (detritus). In the bush they are mostly found on dead vegetation from near ground level to high in trees or tall shrubs, where they sometimes dine on live flowers.

Shown above is a female carrying her egg case (ootheca), which she will hold for some time before dropping it somewhere, hopefully for the young to hatch and mature, but this they do without any parental assistance. Also shown is a moulting Black Cockroach, which initially is not only soft and very vulnerable, but pale and very noticeable, requiring a safe location to perform this function and still survive.  A mature cockroach is quite robust and around 4 cm (13/4") in head/body length.