What do we know about cats? You show them a litter box and they will from that moment on never make anywhere else in the house. Try that with a dog. Cats don’t have receptors for sweets, so you can’t train them by offering them sweet treats. In fact, you can’t train them at all. That’s supposedly because they are too smart to cater to human whims. I don’t know about that; after all, they will chase the beam of a laser pointer ad nauseum, never learning that they cannot catch it.
If you think your cat is affectionate towards you because he or she rubs up against your leg, think again. They are just marking you as their territory, so that if they find themselves in danger, they’ll know where to run for protection. Cats do have a remarkable ability to land on all fours if you toss them into the air, and they are pretty good at catching mice and birds that they will then offer as a present to the household where they happen to be living. If you want to reciprocate to this kindness, you can offer them a little catnip. They’ll immediately turn on their back and wait for some tummy rubbing. Why they respond to the scent of this flowering plant is a mystery since it doesn’t seem to offer any evolutionary advantage. Actually, not all cats are attracted, but roughly three quarters of them are. Some sort of genetic trait is likely involved. Furthermore, only mature cats are attracted, kittens are actually repelled by the scent.
The chemical in the scent of catnip that produces cat euphoria is nepetalactone. The plant does not produce this compound to attract cats. Since cats do not pollinate, and do not eat insects, there is no advantage to the catnip plant to attract felines. So we have to look elsewhere for any advantage offered to the plant by nepetalactone. It turns out that this compound happens to be a pheromone, or sex attractant, for aphids, the tiny sap-sucking insects that can sap the life out of a plant.
Obviously there is no advantage to the plant in attracting aphids. But there is an advantage in attracting aphid predators. The lacewing fly and creepy wasp find that aphids provide just the right environment for laying their eggs and have learned to hunt down aphids by going after the pheromone they produce. The catnip plant takes advantage of this phenomenon and churns out nepetalactone to attract the aphid predators that then lay their eggs inside the live aphids and end up killing them.
While cats love catnip, cockroaches do not. The scent of nepetalactone sends them skittering away. Removing the roaches’ antennae renders them indifferent to nepetalactone, revealing that it is receptors on these rather than on the feet or in the mouth that respond. Nepetalactone also repels a variety of biting insects, including the mosquito. But it’s not a good idea to use an insect repellant based on this chemical if you are on safari. Catnip attracts big cats too. Like lions, tigers and leopards. I don’t think you want these guys rubbing against your leg.
