Feet Sensitive to Sweetness

A butterfly with a black body and white spots with mostly black wings and white spots on the edges, stands on a red flower pistol against a blurry green background

Biological Strategy

AskNature Team

Image: Nicole Köhler / Pixabay / Free non-commercial use

Sense Chemicals (Odor, Taste, etc.) From the Environment

Chemicals are important for signaling and communication among living systems, either intentionally (such as when two living systems try to find one another) or unintentionally (such as when a plant emits a chemical signal that an herbivore can use to find a tasty bite). They are also important for other uses, such as navigating or finding sources for minerals. But chemical signals are often relatively weak and disperse when moving through water or gases. Therefore, detecting them requires specialized abilities, including a way to determine where they are coming from. A well known example of sensing chemicals can be seen in ants following a pheromone trail laid down by others in their colony to locate a quality and abundant food source.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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The feet of butterflies taste sweetness using extremely sensitive taste hairs.

“No matter where they are on an insect’s body, taste sensors normally take the form of hairlike structures called taste hairs. Each one usually has five sensory nerve cells (neurons) at its base, four of which are concerned with taste. Of these, one always responds to sugar, a second to water, and the other two to various salts…Butterflies also have feet that can sense sweetness. When they have been starved, they can detect sugar diluted in water down to concentrations as low as 0.003 percent using their feet. This is a sensitivity 200 times greater than that of the human tongue.” (Shuker 2001:33)