A few weeks ago, my Facebook newsfeed prodded me with this rather distracting headline:
“Mazda 6 recalled over spider invasion!”
Wait, spiders are invading our cars?
I clicked on the link, and learned that a common species of spider, call the yellow sac spider, just loves the smell of gasoline, and this passion for gas leads it to build its home within the Mazda 6 fuel tank. The webs it weaves disrupt the pressure regulation system within the fuel tank, causing it to crack. Gasoline leaks onto hot engine components, and boom! The engine catches on fire.
Engines spontaneously catching on fire? Seems like a good reason to issue a recall.
But as for the reasoning - is it really true that spiders are attracted to the smell of gasoline?
I took a peek into the scientific literature. Gasoline is composed of hydrocarbons, a class of molecules that are built from only hydrogen and carbon atoms (hence the name: hydro-carbon). I searched for any reference that linked spiders to hydrocarbons, and found only one: the East African jumping spider is attracted to the smell of specific species of plants whose nectar is favored by mosquitos; presumably hanging out on the plants gives them greater access to these mosquitos, one of their favorite forms of prey. Some of the compounds that determine the tree’s “smell” are indeed hydrocarbons; however, none of the hydrocarbons produced by the tree match those that would be found in standard gasoline.
Christopher Buddle, entomologist and blogger over at SciLog’s Expiscor blog, was also skeptical of the "gas-loving" spider story. He did his own literature search, and found that some spiders might be attracted to the smell of specific hydrocarbons found in the exoskeletons of bugs - but, once again, none of these hydrocarbons match those in gasoline.
It is a huge leap to say that the yellow sac spider loves the smell of gasoline just because certain other spiders like the smell of certain other hydrocarbons. Buddle believes he has found the source of the story, a 2011 Reuter’s piece in which automotive journalist Mitsuhiro Kunisawa is quoted as saying, “This spider's distinguishing characteristic is that it likes the smell of gasoline, caused by the hydrogen oxide.” As a chemist, I can tell you that “hydrogen oxide” could refer to molecules that are built from hydrogen and oxygen, none of which should be found in standard gasoline.
Perhaps, on the scale of scientific errors, the gas-loving spider story is a relatively inconsequential one: how much does it really matter if a few people believe that spiders enjoy the smell of gasoline? (Though I must say, I have this image in my mind of some future dad, lecturing his sixteen-year old son about a new car : “Now, son, after getting the oil changed, remember to check the engines for spiders! You know how those buggers just love the smell of gasoline.”)
But whatever the consequences, as a scientist and writer it still disturbs me when scientific inaccuracies are hyped and spread. Here is a sampling of some of the headlines I found:
“Petrol-sniffing spiders force Mazda to recall 42,000 cars over fears they could cause engine fires” (Daily Mirror)
“Gasoline-Loving Spiders are Back: 52,000 Mazda6 Units Recalled” (autoevolution)
“Petrol-loving spiders force Mazda recall” (motors.co.uk)
Luckily, many of the larger news organizations (such as CNN) have avoided the “gas-loving spider” story.
Christopher Buddle has attempted to contact Mitsuhiro Kunisawa to see if he has any evidence for this story. For updates, follow Buddle’s blog at http://www.scilogs.com/expiscor/