Why Ladybugs Stink

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20161109a

Convergent ladybug (Hippodamia convergens), a North American species.

If you’ve ever handled a ladybug, also called ladybird, you may have noticed that it sometimes gives off an unpleasant odor.

In fact, when scared, it produces an intensely stinky chemical called pyrazine from special glands on 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). If the beetle gives off the smell while you’re handling it, it’s because it’s taken you for an enemy!

20161109bThe 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 throw 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.

Marking Their Territory

Hippodamia tredecimpunctata larvae

Larva of the thirteen-spot ladybug (Hippodamia tredecimpunctata), native throughout the Northern Hemisphere, surrounded by its prey: aphids.

A ladybug’s feet will also give off pyrazine just by walking around after it settles on a plant to lay its eggs. It’ll do so near a supply of live food for its larvae (ladybugs are predatory and consume such plant pests as aphids, whiteflies, mealybugs, scale insects, mites, psyllids, and small caterpillars). In this case, the role of pyrazine is to warn other ladybugs as well as other predatory insects that the plant in question is its territory and that they would do best to look elsewhere.

And that is not a threat to be taken lightly, as ladybugs also eat the eggs and larvae of other beneficial insects, including those of other ladybugs. Yes, our beloved ladybug can also be a cannibal!

The ladybug make look cute and harmless, but it sure knows how to take care of itself!20161109a

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