We don’t know what your relationship with the smell of sweaty feet is, but we imagine it’s not idyllic. This is because you are human beings and not black widows: if you were male of these spiders you would appreciate the slightly “cheesy” smell of unwashed feet, and you would chase it knowing that it comes from a female who wants to mate. This is according to a study published in Journal of Chemical Ecologywhich demonstrates the importance of foot odor in black widows.
Hunting for smells. The spiders featured in the study are western black widows of the species Latrodectus hesperusnative to the western United States. They are a much studied species in terms of sexual behavior, because they are not difficult to observe and have a mating season that lasts for the entire summer. Sex for these black widows is an important issue, especially for the males: if the females survive the mating season and can mate even the following year, the males usually don’t make it, and are therefore in a certain hurry to find a partner.
How do they do it? Searching for scents: Female Western black widows produce pheromones that are “smeared” on the web, and males follow them until they find a potential mate. Once at its destination, the pheromones push the male to court the female: one of the most used methods consists of cutting pieces of the female’s web and mixing them with his own, to show her that he is not prey (and making the web itself less attractive to rivals). The study by Simon Fraser University, in Canada, focused precisely on these pheromones, to identify their composition and functioning.
Odor (IR)RESISTIBLE. The most interesting discovery of this long analysis, which required a year of field work and months of laboratory analysis on the chemical substances collected from the webs of black widows, has the form of two chemical compounds, with very long names but identified in the study simply as 1 and 7. When 1 and 7 combine, the result is the production (also) of isobutyric acid, the same substance found in butter, in mature cheeses and also in human vomit. This is the substance that gives black widow spider webs their unmistakable foot odor, which males find irresistible.
Summer seduction. The study also found that female spiders produce these pheromones all year round, but intensify their production in the summer months, when there are more sexually mature males available and therefore more competition.
And basically it works like this for us too: putting on a seductive perfume makes sense when there is, so to speak, material available, much less when there is no one around…
