Eyes See 300 Images Per Second

Biological Strategy

Dragonflies and damselflies

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Image: Marie Brochu / Wikimedia commons /

Sense Motion

Perceiving motion is important for a living system to sense where it is in relation to a moving environment, which is critical in locating resources or wayfinding. This applies whether the environment itself is in motion (such as water movement coming from a nearby fish) or the living system is moving within a stationary environment (such as a bird flying through the air). Because motion dampens over distance and the cost of missing those motion signals is high, living systems must be quite sensitive to these signals. For example, fast-flying big brown bats have microscopic, stiff, domed hairs on their wing membranes that act as a sensor array to monitor flight speed and airflow conditions.

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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 eyes of dragonflies sense motion well due to high flicker-fusion frequency.

Image: Piet Spaans / Wikimedia commons /

Somatochlora arctica Northern male Brunssummer Heide Netherlands

Image: Marie Brochu / Wikimedia commons /

Front view of a dragonfly

“Although insects cannot see as sharply as we can, they compensate by being better at sensing motion. The rate at which the eye can distinguish separate static images before they fuse to create the illusion of continuous movement is called the flicker-fusion frequency. Our eyes can see around 50 images per second in good light, less in dim conditions. That’s why movies appear to move even though they are really a series of separate frames. With a flicker-fusion frequency six times faster than ours, dragonflies see 300 images per second, so they would see a movie for what it truly is – a slide show made up of a sequence of static images.” (Shuker 2001:14-15)

Last Updated August 18, 2016

References

Book

The Hidden Powers of Animals: Uncovering the Secrets of Nature

26/02/2021 | Dr. Karl P. N. Shuker

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