Dorothy Hinshaw Patent
Nature’s Animal Ambassador
Take butterflies. Have you ever watched a butterfly flit over a plant, gently touch its feet to a leaf, and then fly on to the next leaf? That butterfly isn’t being picky about where to land. It’s hunting for the right kind of leaf for laying its eggs. It’s “smelling” the leaf with its feet!
Actually, we need to qualify that statement a bit. Some writers will say the insect is “smelling” the leaf while others may write that it’s “tasting” the leaf. Smelling and tasting are forms of “chemoreception,” or sensing of chemicals. Smell usually refers to sensing from a distance while tasting generally means actually touching the nerve cells that sense a chemical.
We humans have cells in our noses that send messages to our brains about chemicals in the air. We call that our sense of smell. We have cells on our tongues that sense chemicals dissolved in liquid in our mouths. That’s taste.
That butterfly doesn’t have a nose, and its mouth is a long tube for sucking up nectar from flowers. Its chemoreceptors are elsewhere, like on its feet, around its mouth, and on its antennae. Most butterflies lay their eggs on the plants that the hatched caterpillars will eat. Some species are very specific about what plants their young can feed on. Take the postman butterfly, which lives in Central and South America. Its caterpillars can only survive on certain species of passionflower vines. Other species are poisonous to their offspring.
The female postman butterfly has dozens of special nerve cells on her feet called “gustatory sensilla.” Scientists think that when she touches gently down on a leaf, these cells can sense chemicals there that would be poisonous to her caterpillars. She avoids laying eggs on those leaves. But when she finds a plant that will nourish her young, she’ll alight and lay her eggs.
Now take your shoes off and move your feet around on the floor. The only nerve endings on your feet are ones that sense touch. But then, you don’t need to be able to smell the ground you walk on. Imagine how gross it would be if your feet could smell the insides of your socks and shoes—yuck!
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