Scent Trails Lead to Food

Biological Strategy

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Send Chemical Signals (Odor, Taste, Etc.)

Tastes, odors, and hormones are all chemical signals that can float through the air or water, or be applied to solid surfaces. Chemicals are important for signaling and communication; even humans, with our underdeveloped sense of smell, are influenced by chemicals more than we realize. Chemical signals are often specific to the living system intended to receive them, and are often relatively weak, dispersing upon moving through liquids or gases. To ensure that chemical signals reach their target, living systems create unique chemical signals and methods of dispersal. One example is an orchid that is pollinated by dung beetles, and therefore distributes a dung-smelling aroma to attract them.

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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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Caterpillars of the European moth find new food sources via scent trails exuded from other caterpillars.

“A European moth that is a serious pest in orchards, lays its eggs in spirals glued together around the twigs of fruit trees. When they hatch, the young caterpillars, while sustaining themselves by eating the leaves immediately around them, spin a large silken shroud around the branch so big that it can accommodate them all. They spend the day within it, concealed from the sight of hungry predatory birds. But when night comes they set out in long columns to demolish more leaves.

“After they have eaten everything in their immediate neighbourhood, a single scout sets out to prospect for more. As it explores new parts of the tree, it lays down behind it a trail of scent that exudes from glands on its rear end. This enables it to find its way back to shelter before dawn. The next night, its companions inspect the trail. If it has a single track, as might happen if the caterpillar was taken in the night by some hunter, they will ignore it. But if there is a double track, indicating that the scout returned and if, furthermore, its smell indicates that the scout had a good meal, then the whole colony of several hundred will set off in procession to strip the leaves from yet another part of the fruit tree.” (Attenborough 1995:58)

Last Updated August 18, 2016

References

Book

The Private Life of Plants

BBC Books | 21/08/1995 | David Attenborough

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Scent Trails Lead to Food

Send Chemical Signals (Odor, Taste, Etc.)