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.

Reference: padil.gov.au

padil.gov.au

Jewel Wasp Or The Emerald Cockroach Wasp

Jewel Wasp or Emerald Cockroach Wasp

Jewel Wasp or Emerald Cockroach Wasp

What a beautiful creature! The metallic blue green body with contrasting orange colour of the 2nd and 3rd thighs! It flies with shimmering wings and when it sits, its antennae dance! It is the Jewel Wasp or the Emerald Cockroach Wasp.

Location: India

Season: Winter, November

Order: Hymenoptera

Suborder: Apocrita 

Superfamily: Apoidea 

Family: Ampulicidae 

Ampulex compressa

More interesting than the external appearance is the behaviour of the wasp. Unlike most wasps which paralyse and eat their prey, the Jewel Wasp paralyses a cockroach and then puts it into a daze in order for its offsprings to grow inside of the cockroach. The wasp uses its neurotoxin rich venom to sting the cockroach twice, both at surgical precision. The twice stung cockroach readily gets the eggs laid in its body, becomes a living meal for the new born larva. How it paralyses the cockroach is a marvel. 

 The female wasp when ready to lay eggs, flies around looking for cockroaches. She sneaks up on an unsuspecting cockroach and subdues it by holding it with her jaws. With one precise sting, she injects venom into the prothoracic ganglion. The venom causes paralysis of the front legs of the cockroach (due to a post synaptic block at the octopaminergic neurons). Once the cockroach is paralysed, the wasp injects her second dose of venom into the cockroaches head, by piercing the cockroach's exoskeleton with her stinger, precisely locating the ganglion in the nervous system and injecting the venom into it. This second sting controls the mind of the cockroach. The head sting induces first 30 min of intense grooming (due to dopamine in the poison), followed by hypokinesia during which the cockroach is unable to generate an 'escape response'. The cockroach now becomes a puppet in the hands of the wasp. The cockroach also looses less water, consumes less oxygen and survives longer. The wasp leads the cockroach to her burrow, by dragging the whole live but paralysed and mind controlled cockroach which is much larger than the wasp herself. The wasp lays a single egg onto the abdomen of the cockroach. She then blocks the burrow to contain the cockroach inside. The mesmerised cockroach does not resist any of this.

The egg hatches into a larva, which chews its way into the cockroach's abdominal cavity and becomes an endoparasitoid. The wasp's larval development, from egg laying to pupation, lasts about 8 days during which the cockroach must remain alive but immobile. The larva thrives by feeding on the cockroach from inside. The larva produces an antibiotic substance to keep the cockroach's insides clean and free from microbial organisms that reside within. The adult hatches out of the by then dead cockroach. 

This chance spotting of the beautiful wasp has taught me a lot!

References:
http://onlinelibrary.wiley.com/doi/10.1002/arch.20092/abstract
http://onlinelibrary.wiley.com/doi/10.1002/neu.20254/abstract
http://www.bgu.ac.il/life/Faculty/Libersat/pdf/JCP.2003.pdf
http://phenomena.nationalgeographic.com/2013/01/07/if-youre-going-to-live-inside-a-zombie-keep-it-clean/