Australian
Screen

Teacher’s notes

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This clip shows the world of the cockroach from the cockroach’s point of view. Magnified images and the sounds of cockroaches provide information about habitat and behaviour and dramatise their activities. Graphics to suggest an X-ray image of the insect are used to illustrate its nervous system. Scenes of a city and human domestic life provide the background to the cockroach world. Shots of a child cleaning her teeth and asleep in bed suggest the busy but largely hidden nocturnal life of cockroaches. The colour film has a voice-over narration.

Educational value points

• The clip provides factual information about cockroaches. All cockroaches have an oval and flattened body shape, a thorax covered by a large plate that extends over part of the head, chewing mouthparts, compound eyes and prominent long antennae. Two spikes extending from the rear of the abdomen, known as the cerci, can sense minute air movements and send signals directly to the leg muscles, enabling the cockroach to rapidly detect and flee from potential danger.

• The behaviour of cockroaches is governed by thigmotaxis, the movement of an organism towards or away from any object, which is motivated by touch. Their impulse is to gather together in large groups in dark places where they can touch as many others of their species as possible. The cockroach has adapted to cities and thrives in warm, moist crevices of buildings. Bathrooms and kitchens in particular provide them with the environment and the sustenance they need to survive.

• There are 3,500 different species of cockroach in the world, but in Australia introduced pest cockroaches account for only 10 of the 400 or so species found, with the most widespread pest cockroach being the small German cockroach. Native Australian cockroaches are rarely encountered in urban areas as they avoid human contact and forage in the bush.

• There are commonly held beliefs that cockroaches are dirty and are carriers of disease, but cockroaches, like most insects, keep their bodies clean for their own protection. There is no definitive evidence of cockroaches transmitting disease, but as they often defecate near the food they eat, any food or surface they walk on will be contaminated.

• It is suggested that, compared with the cockroach, humans may be 'a passing evolutionary novelty’. The cockroach has been on Earth for 250–300 million years, and modern cockroaches are more similar to their ancient fossil ancestors than any other insect in existence today. In contrast, Homo sapiens first appeared around 100,000 years ago. Cockroaches are also more resilient than humans in that they can respond to a threat in 50 milliseconds, and can survive three months without food and 30 days without water. In the case of a nuclear war their relative resistance to radiation means they would outlast humans, even if only for a short time.

• Film language is used in the clip to suggest threat humorously. The tone of the narration, the domestic scene of a little girl cleaning her teeth and other familiar suburban scenes contrast with and augment the perceived threat of the magnified shadow of the cockroach. The enhanced soundtrack of insect sounds and the use of exaggerated language, 'vast hordes’, 'primeval marauders’, contributes to the sense of menace.

• The clip is an excerpt from a nature documentary that seems to parody the David Attenborough style of presentation while presenting factual information. The filmmaker uses visual and verbal humour and a laconic Australian voice-over to convey information about cockroaches in an entertaining way. The script supports this approach by equating cockroaches with humans, and describing them as belonging to the ‘first gregarious community’. The images of the city with the superimposed close-up of a cockroach invite the viewer to see the world from the cockroach’s perspective.

Cockroaches in various urban locations.

Narrator While we are all enchanted with life on the African plains, we dismiss the delights of creatures closer to home. For the roach, humans are just a passing evolutionary novelty, whilst for humanity, they are primeval marauders, despoiling our cities and homes.

When the lights go out, vast herds numbering in the tens of thousands leave their hideaways and start foraging across our fertile domestic landscape.

Cockroaches prefer the humid nights as they are sensitive to water loss. During the drier days they seek moist hideaways. For every roach we see, another 500 or so are lurking. Under fridges and cracks in the walls, they congregate.

The cockroach’s society is not as organised as their descendants, the termites, but they are thigmotaxis, they enjoy being close together, touching one another. Theirs was probably the first gregarious community that evolved on earth.

We assume cockroaches are scared of the light. But they have poor eyesight compared to their major alarm system, the cerci: two small spikes protruding from their rear, where many tiny hairs can sense the faint movements caused by other roaches’ footsteps. Our movements are gale warnings. Signals from the cerci travel through a special elongated nerve cell, directly to the leg muscles. They are escaping a few thousandths of a second before they know why. By bypassing the brain, the roach’s escape system is lightening fast and almost foolproof.