At the age of 36, Adolf Butenandt was awarded one of the 1939 Nobel Prizes in Chemistry for his work on sex hormones. He had isolated and structurally characterized the mammalian sex hormones oestrone, androsterone and progesterone, which all play important roles in sexual development and reproduction. In the year of his award, however, he embarked upon a new endeavour: the first-ever isolation of a sex pheromone (a sexual attractant) from an insect.This proved to be a serious challenge. It took some 20 years, before he and his team were finally successful and he could report the isolation and characterization of what he called bombykol to the Lindau audience. Bombykol is a relatively simple molecule that is released by the female silk moth (Bombyx mori) to attract mates. Despite its simplicity, the molecule is amazingly potent. Butenandt reports, that even if released in 11 kilometres distance to a female, 26 % of male silk moths would still find their way back. Furthermore, if as little as 1,000 bombykol molecules were introduced to containers holding 100 male silk moths, half of the moths would start moving their wings excitedly, Butenandt says, implying that only a few molecules are sufficient to trigger a reaction. Even today (2013), this stunning sensitivity is unmatched by any form of modern analytical instrumentation at our disposal. Our own olfactory system is equally outclassed by the silk moth: the lowest concentration of an odorant detectable by the human nose is about 0.01 nanomol , which corresponds to around six trillion molecules in a litre of air. The 20 years it took Butenandt and his team to isolate bombykol from female silk moths shows, that obtaining sufficiently large quantities of such natural products can be a cumbersome task. In the case of bombykol, 500,000 female silk moths were processed to obtain merely 15 milligram of substance. Notably, this minute quantity was sufficient for a complete structural elucidation. For the pigment xanthommathin, things looked slightly better. Here, 100 milligram could be isolated from the wings of 10,000 moths and another 19 milligram from the eyes of 7,800 blowflies. In any case, a lot of patience is required for this kind of work. One of Butenandt’s motivations for studying insect pheromones was the idea, that they might be used as a way of controlling insect pests. Luring the males away from agricultural areas using pheromones and killing them could be a way to avoid a further spread of the insect plague, Butenandt suggests. And indeed, he should be proven right. Today, hundreds of pheromones have been isolated from various insects. Several of these compounds are used for pest control, covering areas of at least 10 million hectares . Contrary to classical pesticides, pheromones are usually non-toxic, can be used in very small quantities and are highly species specific. The pheromone-based pest control envisioned by Butenandt is hence considered a very “elegant” technique, despite some of its drawbacks (it usually only affects males and does not kill the insects instantly) . The present lecture is the second-last Butenandt ever gave in Lindau. In 1961, he should talk about insect pheromones once more. In the years to come, until 1992, three years before his death, Butenandt participated without speaking himself. With 31 visits to Lindau, he holds the record of most participations amongst all Nobel Laureates. David Siegel D Purves, GJ Augustine, D Fitzpatrick, et al., Neuroscience, 2nd edition, Sunderland (MA, USA), 2001. P. Witzgall, P. Kirsch, A. Cork, Journal of Chemical Ecology 36 (2010) 80.