Cockroaches: the world’s most annoying insect?

Posted: December 30, 2014 in Science
Tags: , , , , , , ,

We're coming to get you.

We’re coming to get you.

The Wellthisiswhatithink household has been experiencing a sudden rush of cockroaches. (Insert horrified scream at regular intervals here.)

This is an unusual infestation for us. We frequently have to deal with invasion of ants (whenever we get consecutive days of rain they move indoors) and sometimes mice (now seemingly dealt with by chucking inordinate amounts of “Ratsak” into the cavity under the house). Mice and ants frequently reach plague proportions in Australia. But we have, thus far, seen very few ‘roaches, until this year. This year, it seems every time we move an item, something dark and vaguely menacing scuttles rapidly away.

When you think of cockroaches, you’ve got to admit you think filth and squalor. Certainly Mrs Wellthisiswhatithink does. She is mortified at every appearance.

But are these traditional beliefs that cockroaches are dirty, disease-spreading bugs actually entirely accurate? As always, the worldwideinterwebs thingy is our friend.

Apparently there are nearly 4000 species of cockroaches in the world, but only 25 to 30 actually have a pest status.

And yes, cockroaches love to live in filth — but does that make them dirty?

You want to know why we like big spiders in Australia? This is why.

You want to know why we like big spiders in Australia? This is why.

An interesting test has just been completed to see just how dirty cockroaches are in relation to a human being and other things we have daily contact with.

The researcher took two swabs of germs. Firstly, a cockroach will run across a dirty surface, such as the kitchen floor, and will then be left for two hours before a swab is taken of its’ er, feety little things. The a human set of fingers will then walk across the same surface and he won’t wash his hands for two hours before his swab is taken.

Both samples are then put into separate Petri dishes, then turned upside down and put into an incubator at 37 degrees to be left overnight. If there are any germs, they’ll easily be seen in the morning.

Twenty-four hours later it’s time to compare the cultures to find out who’s the king of clean.

First swab: a control swab was added to the experiment to guarantee the experiment is accurate. There is no bacteria growing on this plate.

Cockroach’s swab: There are a few colonies of bacteria there.

Human swab: There’s a lot more bacteria on the plate where the human hand was swabbed.

The cockroach is actually cleaner than human.

Why? Because cockroaches actually clean themselves fastidiously — all the time.

“Most species of cockroaches are kind of like cats. Cats are considered to be a very clean animal because it’s always grooming itself. And cockroaches do that also,” says bug collector Darrin Vernier. He lives in the US state of Arizona and is crazy about creepy crawlies.

Darrin’s got 10,000 roaches in his personal collection and he claims that his roaches are invaluable in breaking down dead and decaying matter in the eco-system.

So cockroaches could be seen in the insect world as the obsessive compulsive fastidious cleaner?

Darrin says this is a great way to look at it: “Sometimes I walk in from the outside and I track in dirt under my feet accidentally. That’s really the only thing the cockroach does that has any relation to filth at all and it’s because we’ve already left it there. If we clean it up it’s not a problem.”

So if roaches are so clean, what sort of dangers do they really pose?

Dr Noel Tait is an honorary professor in invertebrae zoology at Macquarie University. He says the problem with cockroaches are those nasty little deposits they leave behind.

“The allergens are cockroach allergens themselves. They are in the faeces because they are chemicals from the bodies of the cockroaches. And people who are susceptible to allergic situations can become hyper-sensitised to them,” says Dr Tait. So regular cleaning reduces the possibility of an allergic reaction to roach faeces. (Reaches for a Chux and the disinfectant.)

There are no available Australian statistics, but in the United States, up to 60 percent of asthma sufferers are affected by cockroach allergens.

If you’re one of them, you could get skin rashes, watery eyes, nasal congestion and even asthma attacks.

Cockroaches can, indeed, spread disease. And even quite frightening ones, like salmonella, staphylococcus and even leprosy. Entomologist David Rentz says the dirtiness of a cockroach is entirely dependent on where it has been.

“Studies have shown that they pick up these things on their feet and move them around that way and when they are feeding, of course they get bacteria and such on their mouthparts,” he said.

“If they have not been any place where they can get germs, well they are not germy at all.”

Luckily most homes are free of really nasty germs. A quick whizz round with an airborne disinfectant spray will help.

Dr Rentz is quick to point out that it’s only the six or eight introduced species of cockroach in Australia that are worth killing.

The more than 500 species of native Australian roaches are unlikely to survive long in an urban environment and are important to the native ecosystem.

“It’s just a very small percentage of the total number of cockroaches that give the whole group a bad name,” he said.

womanscream

So if you don’t want cockroaches taking up residence at your house — clean up. Cockroaches in homes are only as dirty as the environment they are living in. If you have a filthy house, they will spread that filth around your kitchen, but if your kitchen is clean and hygienic, you won’t be providing them with a food source and they won’t bother so much. But if the odd cockroach does show up, at least you know they’re not that bad. They’re actually quite hygienic.

Cleaning up regularly is the best bet. Chances are the roach will be hungry and go looking for richer pickings next door.

Some common cockroach hiding spots.

Start by attacking these areas with a combination of insecticide (the barrier kind will help) and loads of hot soapy water and a broom.

Cockroaches thrive in warm, humid conditions. They prefer to live in kitchens and other food preparation areas, so they can feed off food spills. But cockroaches can eat just about anything, and can survive without food for long periods of time. Cockroaches are scavengers. While most roaches prefer sweets given a choice, in a pinch, they will eat just about anything: glue, grease, soap, wallpaper paste, leather, book-bindings, or even hair. Worse yet, a cockroach can survive a remarkably long time without food. Some species can go as long as 6 weeks without a meal! These traits make cockroaches in our homes tough to control. But in nature, cockroaches provide an important service by consuming organic waste. They’re the garbage collectors of their habitat. So patience in getting rid of them helps, too.

Hiding spots for the household cockroach include:

  • Cracks in walls.
  • Confined spaces, such as behind the refrigerator, in a pantry or underneath a stack of magazines, newspapers or cardboard boxes.
  • Any furniture items that are generally left undisturbed.
  • Kitchen cupboards.
  • Below sinks.
  • Around water heaters.
  • In drains and grease traps.
  • Gardens.

But what about the one about cockroaches being able to survive a nuclear war? Well, it’s true, they can. For humans, a lethal dose of radiation is about 800 rems but some roach varieties can withstand doses up to a hundred times bigger, and as long as they’re not in the blast zone, they’d survive the radioactive fallout of a nuclear explosion.

As Fruit Of One’s Loins remarks, “that’s just creepy; that’s why I hate them”. (Cute horrified scream and gallons of soapy water.)

roach panSo how to deal with the sudden appearance of a cockroach in your life?

Chances are a rolled up newspaper or a fry pan won’t cut it. Those little suckers are fast. Measurably fast.

Cockroaches detect approaching threats by sensing changes in air currents. The fastest start time clocked by a cockroach was just 8.2 milliseconds after it sensed a puff of air on its rear end. Once all six legs are in motion, a cockroach can sprint at speeds of 80 centimeters per second. And they’re elusive, too, with the ability to turn on a dime while in full stride. Whacking them with a sizeable burst of insect spray will give you a better chance.

Except the little buggers often scuttle off anyway. Are they resistant to that, too? They’re superhero insects.

Perhaps most fascinatingly, cockroaches can be conditioned. Russian physiologist Ivan Pavlov first documented the concept of classical conditioning, famously demonstrated by his salivating dogs. The dogs would hear a ticking metronome each time they were fed. Soon, the sound of the metronome alone was enough to make the dogs salivate in anticipation of a meal. Now Makoto Mizunami and his colleague Hidehiro Watanabe, both of Tohoku University, have found that cockroaches can also be conditioned this way. They introduced the scent of vanilla or peppermint just before giving the roaches a sugary treat. Eventually, the cockroaches would drool – yes, drool – when their antennae detected one of these scents in the air.

We are currently working out how to use this information to rid us of urban cockroaches once and for all by creating a new roach trap which will excite them into getting caught all on their own, and which will make us millions. Watch this space.

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Comments
  1. Victo Dolore says:

    I am going to have nightmares now. When roaches appear around here they are about the size of a child’s fist. Stomping on them causes a crunch sound and subsequent splatter pattern that is almost as disturbing as the roach’s presence itself. (Shudder)

    Like

  2. shatara46 says:

    Fabulously good and funny read – thanks, loved it! Here in our “cold” Canada, roaches, cocked or not, don’t seem to be a problem. Don’t think I’ve ever even seen one.

    Like

  3. Woody says:

    I’m glad the testing was done as you’ve described it. One can see how they constantly clean themselves, but it only looked like its fore-limbs and mandibles at work (what about the rest of its body?). But if well designed and controlled testing shows that they are far less germy than us, then as a sceptic, my view on the subject must adjust to reflect the new evidence I am exposed to.
    Thanks, dispassionate investigation is where it’s at !

    Like

  4. Ummm….yuck and yikes.

    Like

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