Welcome to another instalment of urban [pest] myths with Matt. This time I’m looking into the history of the oldest chestnut in the book: ‘roaches versus bombs’. This one is quite tricky and needs to be broken down a bit to be investigated. First question is: Why cockroaches? Why not locusts or wasps for example?
“It’s not easy to figure out where this idea or cockroach radiation resilience originated.” and“…couldn’t find any obvious references to post-blast investigators noting the presence of unperturbed roaches at ground zero”
So said Prof. May Berenbaum in her 2001 article ‘Rad Roaches’, which is a good place to start the search for facts behind the claim. The paper trail for bringing the concept of cockroaches surviving an atomic bomb detonation is fairly easy to follow, but the origin is harder to determine. In 1962, H. Bentley Glass, a John Hopkins University geneticist, told the New York Times that in the event of nuclear war, “the cockroach, a venerable and hardy species, will take over the habitations of the foolish humans and compete only with other insects or bacteria.”
Later, in 1968 The New York Times followed it up with another article about cockroaches inheriting the earth that included the snappy line: “A nuclear war, if it comes, will not be won by the Americans â€¦ the Russians â€¦ the Chinese. The winner of World War III will be the cockroach.” I’m sure it made for pleasant reading over breakfast.
With this sort of coverage the mental image of cockroaches and nuclear bomb was bound to stick in the public concious but where did the idea stem from? As with my previous expose of termites’ love of rock music, Google Books offered a surprising line of investigation in a publication that Prof Berenbaum may have missed, namely the esteemed journal of: Astounding Science Fiction, Vol. 39 No. 5 July 1947.
This particular volume contains a short story entitled ‘The Figure” by Edward Grendon. In this tale (it’s on page 92 and doesn’t take long to read), a group of scientists are assigned to investigate time travel “to find out about the cockroaches.” Furthermore: “It didn’t make the papers, but about a year after the New Mexico atom-bomb test, the insect population at the testing ground suddenly increased a hundred fold.” An interesting premise for a Sci-fi story so far, but then the author goes on to, possibly, start something big…
“New Mexico was nothing to Hiroshima and Nagasaki. After all there are comparatively few “true bugs” (sic) in the desert and a great many in a Japanese city. About a year after Japan got A-bombed, they really swarmed out of the cities at the same time. They came out suddenly one night by the millions. It’s been estimated that they killed and ate several hundred people before they were brought under control.”
Edward Grendon clearly didn’t have a lot of entomological training (or access to the Rentokil Pest Guide- quick plug!) when he wrote this, as he freely interchanges the terms bug, cockroach and beetle to mean the same thing. He also gives cockroaches the sort of swarming behaviour that you might see with wasps or locusts. I think there’s some grounds to think that this short story might have had a bit more impact than folk have since given it credit for, but is there any substance to the story? For that, we need to understand how atomic bombs cause death.
An atomic bomb “explodes” by producing a massive volume of gas from a small volume of solid matter. Organisms die through immediate impact of the expanding gas wave, impact of shrapnel and debris, or by direct thermal burning.
Thermal radius (sufficient to cause lethal burns) – 2.46KmThe blast of the expanding gas wave can be enough to kill a person.
There have been a thankfully small number of atomic bombs detonated. Based on published figures, for a 15 Kiloton bomb like the ones dropped on Hiroshima and Nagasaki the blast radii for these effects would have been, roughly:
- Blast radius (sufficient to cause impact to kill a human) – 1.98Km
- Radiation radius (sufficient to kill an average human) – 1.14Km
The most modern nuclear bombs like those that have just been disarmed, weigh in at 9 Megatons. For a 9 Megaton bomb, those figures rise to: 1476Km, 1188Km and 684Km respectively. Sobering isn’t it?
Cockroaches and humans have different biology and ecology though, and this must be taken into account as these bomb are designed to be air detonated to kill as many humans as possible. Cockroaches live below ground or in otherwise cryptic hiding places which make them less likely to be affected by the thermal and blast damage from such weapons. Living below ground will also help them survive the effects of radiation. Radioactive metals in the bomb will combine with soil particles from the blast and fall as a suface layer. This is a key difference between conventional explosives and a nuclear bomb, the radioactive particle remain a serious hazard to health long after the immediate effects of the blast.
Given enough time, the radioactive metals will decay past a point they are harmful to life. American cockroaches (Periplaneta americana) can live for approximately 30 days without food or water, after which time the risk of death from radiation causing cellular damage would be much reduced. Which leads us to the final piece of the puzzle are cockroaches immune (or highly tolerant) to radiation?
In 1919, Dr. W. P. Davey did some interesting experiments on confused flour beetle whilst working for General Electric Coproration. He found that low doses of X-ray radiation actually increased their lifespan. Knowing this snippet of information it’s easy to see how a Science Fiction writer could arrive at a story. Flour beetles don’t have the same appeal as cockroaches and there are a lot fewer of them around. Cockroaches, on the other hand, are a first-choice creepy insect to be found in a city.Cockroaches do indeed have a much higher radiation resistance than vertebrates, with the lethal dose perhaps 6 to 15 times that for humans. Whilst impressively more resiliant than us they are not exceptionally radiation-resistant compared with other insects, including the fruit fly or the confused flour beetle.
However, when taking into account the longer term effect of radiation, cockroaches undergo incomplete metamorphosis (shedding their skins to grow into bigger versions with the same shape) several times until they reach adulthood, rather than the complete metamorphosis seen when a maggot pupates into a fly or a grub pupates into a beetle. Juvenile cockroaches would shed radioactive material as the aged, reducing the risk of prolonged cellular damage.
Can cockroaches survive a nuclear blast? Not directly. Their physiology means they have a greater chance of surviving a blast from a much closer distance to ground zero than humans or any other vertebrate has. In addition, their subterranean and cryptic habits will probably see them surviving at distances that would kill other more radiation tolerant, but habitually more exposed insects