Smoking is neither cool nor clever... sometimes

Most non-smokers will probably agree that the smell of cigarette smoke is fairly repulsive - there’s little worse than being stuck in a bus shelter with someone who doesn’t appreciate the finer points of the smoking ban. But scientists from the Max Planck Institute for Chemical Ecology in Germany have found that the tobacco hornworm (Manduca sexta) makes use of a similar effect to defend itself against predators - by exhaling nicotine at them.

Nicotine is toxic (it blocks the signalling between nerves and muscles) and so is used by some plants as a deterrant against herbivores. _Manduca sexta _feeds on wild tobacco plants which contain nicotine, but can tolerate the compound at levels lethal to other insects.

The team identified a gene responsible for directing a small amount of nicotine from the insect’s gut into its hemolymph (the circulatory fluid - insects don’t have blood). The scientists found that this gene allows the hornworm to exhale some of this nicotine through its spiracles (tiny holes which allow air in and out of the respiratory system) and into its headspace in order to deter predators.

By gluing tiny sensors over the spiracles of hornworm larvae, they were able to measure nicotine emissions in larvae which had this gene knocked out. Not only did they find that that these larvae had lower nicotine emissions, but also that they were preyed on more often by the insects’ natural predator, the wolf spider.

They say you swallow up to four spiders in your lifetime while you sleep. That’s almost certainly a myth, as it’s not very likely that anyone even swallows one. But in light of this new reserarch, perhaps it’s even less likely if you’re a smoker.