That seems very odd to me. Are there any other such hoses in other vehicles that have a similar design? I wouldn't expect the spiders to be attracted to the hydrocarbon emissions of gasoline, although stranger things have happened; I agree that you'd expect this to be a less specific problem than it is reputed to be. My first guess is that this is based on coincidence more than anything. A number of spiders look for enclosed places like tubes to make their shelters, and I'd wonder if these things were noticed at certain times of year - how many affected cars were there, and what sort of conditions were they in when this was noticed? For that matter, how was it noticed, and did they identify the spiders or just find a silk shelter tube? There's almost no actual information in any of the notices I could find, just a lot of the normal media hype and wild speculation based on nothing.

Yellow sac spiders are attracted to petroleum by-products, even old fuel cans can become targets.

As for the Mazda, it is just the design of the tank purge valves.

The spiders web the vents, often blocking them, causing fuel delivery problems.

From the spiders perspective, my only conclusion is the fuel vapors sway pheromones that confuse the spider. Some cobweb spiders like widows are even attracted to old grease and oil, likely why you often find widows under old cars that sit long times.

Ask a Mazda dealer what they do to correct the recall condition. My guess is that it could only be the material in the fuel lines.

Only a particular spider (the American yellow sac), is attracted to the evaporative fuel lines of a particular model (The 2009-2012 Mazda 6 sedan with a 4-cylinder 2.5L engine). The V6 version is not affected, neither is the Mark 1. What do you think the fatal attraction is?

I've had a few ideas myself, but I then shoot these down due to the fact that a lot of modern cars use very similar systems, so the problem should be widespread. If it was a particular octane of fuel causing the problem, the hydrocarbons from the petrol would be given off by other cars too.

Maybe it's something to do with the diameter of the lines, or the pipe materials give off a chemical signature smell that confuse the spiders. Another theory of mine has to so with the fact that the 2.5L has a different grill, which could be a little too pleasing to the eyes of the spider. It's something to do with the golden ratio of 1.61 used in art, (classic example is the spiral staircase inspired by seashells). So maybe there's something about the car shape that's attractive to egg-laying or web building.

I'd like to see the stats collected about the cars found with the problem, to see if there was any correlation to paint tint. David Attenborough is the only person who could solve this one. If he can't, the only logical conclusion is that yellow sacs are in fact aliens in disguise, using reliable transport to take over the continent, waiting for their moment.....! Mazda might have to start making uglier cars!