Catnip evolved to repel insects, and about a third of cats ignore it
The chemical that sends cats rolling and purring is not really aimed at cats. Nepetalactone, the key compound in catnip, most likely evolved to keep plant-eating insects away, and it repels mosquitoes, cockroaches and termites. Roughly a third of cats are unmoved by it, and the trait runs in families.
Catnip, Nepeta cataria, is a short-lived member of the mint family with square stems, grey-green hairy leaves and small, fragrant white-to-pink flowers dotted with purple. It grows 30 to 100 centimetres tall and is native to southern and eastern Europe, parts of the Middle East and Central Asia, but has spread widely, reaching 48 US states and New Zealand, where it arrived in 1870. Linnaeus formally named it in 1753; cataria means of cats, from the medieval herbalists' herba cattaria. The word catmint dates to about 1300, while catnip first shows up in colonial Pennsylvania in 1775.
Cats smell nepetalactone through the olfactory lining of the nose, not the specialised vomeronasal organ some animals use for pheromones. A typical reaction to bruised leaves involves rubbing, rolling, pawing, licking and chewing, sometimes drooling, leaping about or growling, and lasts roughly 5 to 15 minutes before the nose tires. Kittens under six months often show no response. Early work suggested a single dominant gene, but a larger 2011 study of 210 cats pointed to many genes acting together. Leopards, cougars, servals and lynxes react much like house cats, while lions and tigers are inconsistent.
The insect-repelling role has been suggested since at least a paper in Science linking nepetalactone to similar defensive compounds made by insects themselves. Iridoids that rub off onto cats from catnip and silver vine leaves repel mosquitoes, and one catnip compound attracts lacewings that eat aphids. Distilled catnip oil has outperformed DEET as a spatial repellent in some research, though it did less well on skin.
Gardeners value it as drought-tolerant and deer-resistant, and it draws butterflies. It was long used as a folk remedy for indigestion, fevers and nerves, and is still brewed as a tea, though modern medicine has largely set it aside.
Source: Catnip
