The cockroach

Oct 05, 2008 Features / Columnists, Interesting Creatures in Guyana

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Cockroaches or simply roaches are insects of the order Blattaria, a name which derives from the Latin word for cockroach ‘blatta’.

There are about 4,000 species of cockroaches of which 30 species are associated with human habitations while approximately four species are well known as pests. However, this insect species lives in a wide range of environments around the world.

It has been discovered that pest species, especially of cockroaches, adapt readily to a variety of conditions but prefer warmth found within buildings.

Many tropical species prefer even warmer environments and do not fare well in the average household.
Cockroaches are most common in tropical and subtropical climates. Those that opt to be in close association with human dwellings are widely found around garbage or in the kitchen.

They are generally omnivorous with the exception of the wood-eating genus which are in fact incapable of digesting cellulose themselves but have symbiotic relationships with various protozoans and bacteria that digest the cellulose, allowing them to extract the nutrients.

The similarity of these symbionts to those in termites is of such that it is believed that some cockroach species are closely related to them.

This insect species is regarded as one of the larger insects with most reaching at the least about the size of a thumbnail although several species are much bigger.

The largest recorded cockroach is the Australian giant burrowing cockroach which can reach 9 centimetres in length and weigh more than 30 grammes.

The spines on their legs were earlier considered to be sensory but observations of their locomotion on the sand and wire meshes has demonstrated that they help in movement on difficult terrain, a trait which has been an inspiration for robotic legs.

Cockroaches leave chemical trails in their faeces as well as emitting airborne pheromones for swarming and mating. It is said that other cockroaches will follow these trails to discover sources of food and water and also discover where other cockroaches are hiding.

Some species are capable of remaining active for about a month without food or are able to survive on limited resources like the glue from the back of postage stamps.

Researchers have also deduced that some can go without air for 45 minutes, a situation which will not even slow down their heart rate.

According to some speculations, there is a possibility that cockroaches could inherit the earth if humanity destroys itself in a nuclear war because they have a much higher radiation resistance than vertebrates.

Their ability to withstand radiation better than human beings can be explained in terms of the cell cycle. Cells are most vulnerable to the effects of radiation when they are dividing.

It is said that a cockroach’s cells divide only once each time it moults, which is weekly at most in a juvenile roach.

And since not all cockroaches would be moulting at the same time, many would be unaffected by an acute burst of radiation, but lingering radioactive fallout would still be harmful.

Cockroaches, like all insects, breathe through a system of tubes called tracheae which are attached to the spiracles, excluding the head.

As such, they, like most other insects, are not dependent on the mouth and windpipe to breathe. While cockroaches do not have lungs and do not actively breathe in the vertebrate lung manner, in some very large species the body musculature may contract rhythmically to forcibly move air out and in the spiracles, a process which may be considered a form of breathing.

Like all insects, the cockroach’s nervous system is decentralized, with some functions distributed in the ventral ganglia. Though decentralized, the insect’s nervous system is fundamentally similar to that of vertebrates in terms of development, structure, and mechanisms of function.

A decapitated cockroach can still walk and show responses to stimulation of its legs, as can a spinal-transected cat on a treadmill. However, a cockroach can survive complete decapitation for up to several weeks before dying of starvation or dehydration.

Cockroaches are known to take special care of their eggs, with the female opting to carry around egg cases on the end of their abdomen which can hold about 30 to 40 long thin eggs.

The eggs are hatched from the combined pressure of the hatchlings gulping air and are initially bright white nymphs that continue inflating themselves with air and harden and darken within about four hours.

It is said that a female produces up to eight egg cases in a lifetime which could result in the hatching of about 300 to 400 offspring.

Of note too is the fact that a female cockroach only needs to be impregnated once to be able to lay eggs for the rest of her life.

These winged, home intruders are also famous for making a hissing noise, although some are known to make chirping sounds instead.

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