Have you ever held a ladybug, and noticed a little bit of yellow excrement on your hand afterwards?

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That would be a revolting-smelling liquid that ladybugs release from their legs, as a defense mechanism! This very smelly chemical is called pyrazine, which is secreted from its feet. Pyrazine’s role is to scare off predators and to advise them they’d better think twice before trying to eat the ladybug (pyrazine not only smells bad, it has a very unpleasant taste). This is their warning to predators when they feel threatened or attacked, and warning that they won’t taste so great if consumed. This excrement is harmless to humans, but can be detected by the human nose even in small amounts.

 

According to Larry Hodgon’s World, the odor of pyrazine is so dominant and persistent that if a ladybug is accidentally crushed while harvesting grapes, the wine produced from it will smell so bad it has to be thrown away. This effect even has a name: ladybug taint. That’s why wineries take great care to gently discourage ladybugs from settling on their vines just before harvest.

This excretion has a revolting smell, which, according to c&en (2007) by Sophie Rovner, the overall smell is a mixture of nutlike, green bell pepper, potato, and moldy odors. The contributors to the foul smells are among 38 compounds, which include methoxypyrazines, which are potent odor-producing compounds found in other animals and plants.

It is also found that orange ladybugs release more of these compounds.