You may not like this, but cockroaches are a lot like us!
Some swear that cockroaches attack people. It’s true that they sometimes rush towards us. Are they in fight mode or in flight? Realistically, they probably see your shadow, a grey mass on the floor, and run towards it to hide. Cockroaches like dark places, even if it isn’t smart for a vulnerable bug to lunge at a deadly foe.
That anomaly aside, roaches are rather intelligent. A Free University of Brussels study of the insects revealed they have social structures and a collective intelligence, which means they communicate with each other to share information on things like where the best food sources are and which places are safe. Although they can function alone, they prefer company and will settle down in a new place if other members of their kind are present. Like us, they also have personalities, and so some are shy, some cranky, others very brave.
Cockroaches are thigmotactic, which means they prefer to spend time in confined spaces where their body is in contact with surfaces all around, says Raja Mahendran, an expert in urban and agro pest control who has worked in leading pest control organisations worldwide.
There are over 400 species — some as large as the palm of your hand. But only two are household pests in Sri Lanka — the American cockroach (Periplaneta americana), the large dark brown ones, and the German cockroach (Blattella germanica), the smaller yellowy brown ones mostly found in commercial kitchens. Worldwide only about five species are pests; the others don’t bother people.
The domestic roach’s survival abilities are legendary. “They once said a nuclear holocaust would kill all but the cockroaches,” says Mahendran. “That’s because they are always in cracks and crevices, so even if you spray insecticide everywhere, you could miss them because they are securely hidden.”
The ultimate survivor
A UC Berkeley study showed that the American cockroach could squeeze itself through thin joints and seams just one tenth of an inch in less than a second, and run through crevices much flatter than their height at high speed. The study also found they can withstand forces nine hundred times their body weight without injury.
The American cockroach has also entered the Guinness book of records for its record running speed of five feet per second, the fastest insect speed in the world. To cap it, they were found to run fastest on their two hind legs – they become bipeds if necessary. The cockroach’s egg pouch is extremely strong and impermeable to pesticides. You can spray them, but the pouches will survive to hatch later, the larva will emerge and in a few weeks reach adulthood. Each pouch of the American cockroach may carry 15 to 20 larvae, so they breed fast. The German cockroach’s egg pouch carries about 50 eggs.
They can be deadly
Fascinating though they might sound, cockroaches can be deadly. Active at night, they feed on almost anything edible; even your toenails, fingernails or eye lashes while you sleep. Or anything else in a room — all types of foods, cardboard, book bindings, clothing, inner lining of shoe soles, their own cast off skins, other dead or dying cockroaches, sewage, sputum and rotting food. As they eat, they vomit partially digested food and excrete faeces. In the process, they spread not only germs that cause disease but the eggs of parasitic worms. If there’s a roach infestation, you’ll see them all over the kitchen when you switch on the light at night. The old method of cockroach pest control, spraying, is still carried out today, usually on commercial properties, says Mahendran.
Today, pest controllers have to think like the pests they are trying to control, says Mahendran. They have to figure out where they would hide and nest. Taking the bait to the insects works better than spraying them. The pest professional is likely to bring along a pen-sized syringe filled with a chemical gel that is a food attractor for the insects and leave drops in the crevices and corners that the creatures inhabit. The roaches come, eat it and carry it away to distribute it to other roaches, with dire consequences for the community. So the new method has a domino effect. It is also less intrusive.
Solutions are getting smarter
Cutting-edge control methods include the use of robotic cockroaches invented to infiltrate cockroach communities and influence and even alter the insects’ behaviour. The mechanical “roach” is built to smell like the real thing, and because roaches recognize each other through the scent of pheramones rather than sight, these little machines are able to mingle with and influence them. Researchers have found that robotic roaches can, for example, cause entire darkness-loving cockroach communities to migrate to dimly-lit environments.
“At first, they were actually going to use a cockroach lookalike robot,” says Mahendran. “But then they found that the robot didn’t have to resemble a cockroach. It could be rectangular like a little flat battery, but smell like a cockroach – pheramones are the key to cockroach communication and so they have synthesized danger pheramones, attracting peramones and so on into the robots so that the robots can wander into the insect community and make the creatures feel fuzzy and warm towards it and lead them to where the pest professionals would have them go.”
That’s usually to their doom.
How they survive
Do these creatures adapt to the poisons and techniques and become smarter or stronger?
“There are three things that affect them: behavioural factors, immunity and resistance,” says Mahendran.
“Resistance means that even before the chemical is invented, there may be two out of a hundred cockroaches – it’s also applicable to other pests – who are immune to its effects. There is something about them that the chemical is unable to affect; it could be genetic. So if there are a hundred you spray on, ninety eight will die and the two will survive. You are unaware that they have escaped. They breed and the new generation also has natural immunity. So, the next time you bring the same chemical spray, the others die, but those with natural resistance don’t. That’s why it’s important to change the class of chemicals that you use. Don’t change the brand, change the class,” he says.
“It could also be behavioural factors. Shy cockroaches may stay in their holes and not venture out, thus avoiding the spray altogether. There may be some who just do not fall for the bait.
“Then there is the immunity problem, which is not the same as resistance. Some don’t get the full dose but just enough traces to develop immunity. If then you apply the right dose on them, they don’t die. But if you increase the dose, they will. The resistant ones don’t die if you increase the dose.”
Insecticides are highly regulated and cannot be developed and sold by just anyone. Sri Lanka’s regulatory body is the Registrar of Pesticides under the Department of Agriculture. The Registrar is very strict and it takes almost a year to get a product passed.