Preying Mantis Eyes
Preying mantises Sphodromantis viridis
are amazing predators, and often found lurking in bushes at
this time of year. They will eat any insect or
arthropod that ventures too close to these watchful compound
eyes. Notice how the insect can rotate its head to get
a better view of potential victims or a possible predator of
the mantis (such as a bird or person). Click on each
image for a larger view of the preying mantis.
Insect eyes are compound eyes, unlike human and other
vertebrate eyes. The external eye contains tens of
thousands of external receptors called omatidia.
Each omatidia consists of a tube that is oriented
toward the outside surface of the eye spheroid. A
separate photo receptor lies at the base of the tube.
These eyes resemble vertebrate retinas - but on the outside
of the eye, not at the focus of a single lens. Insects
see images without lenses. Each omatidium has
a unique direction in space, so the insect with such large
eyes can see in almost every direction.
These images are different views of the same
mantis. Notice the pupil-like dark spot on each
image. This is called the "pseudo pupil". To the
camera or human viewer a small area of omatidia are
oriented along the viewers line of sight. Since we (or
the camera) see directly into the base of the selected omatidia,
we see darkness, not the walls of the omatidium.
Notice that the location of the pseudo pupil is in a
different part of the compound eye for each of the photos
above as the camera has a different angle relative to the
insect's eye. For catching other insects for prey, the
mantis' eyes are highly developed. We cannot see the
individual omatidia in the mantis eyes, whereas most
insects' eyes have much larger and noticeable omatidia.
This corresponds to a digital camera with more pixels.
The mantis has high resolution vision. Because of the
omnidirectional nature of insect compound eyes, most insects
do not turn their heads to "focus" on a particular
object. Because the mantis can rotate its head, I
suspect that the insect has a special region of more highly
sensitive and concentrated omatidia, similar to the fovea
in human eyes that are absent in most animals.
This mantis was alive for all these photos and was
allowed to continue lurking for its dinner.
A dead dragonfly's eyes were featured in an earlier Physics
Photo (Nov. 18, 2011).
Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us. Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to firstname.lastname@example.org.
All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion. These photos and discussions may be used for private individual use or educational use. Any commercial use without written permission of the photoprovider is forbidden.