ommateum

[ommateum]

Visual Moodboard

Medium Brainstorm

Analog Collage

Photomontage

Double Exposure Photography

Poster

Mix-and-Match book

Glasses/Headpiece

Projection

Mirror Installation

[ommateum]

Brainstorm

Initial Ideas

The compound eye of insects offers rich visual inspiration. The fractal-like structure, repetition of patterns, and interplay of light could be interesting to explore. It also connects to themes like perspective, perception, or the multiplicity of vision.

Key Words

Pixels

Hexagon

Telescope

Fiber Optic Cable

Resolution

Focus

Photosensitive

Refractive

Perspective

Point of View

Visual Field

Ultraviolet

Polarized light

Expressions

“Bug Eyes”

“Eyes are the Window to the Soul”

“An Eye for an Eye”

“Eye of the Storm”

“Sight for Sore Eyes”

“See Eye to Eye”

“Birds Eye View”

[ommateum]

The Insects: An Outline of Entomology

Insect Vision

In insect eyes, the photoreceptive structure is the rhabdom, comprising several adjacent retinulae (or nerve) cells and consisting of close-packed microvilli containing visual pigment. This signal is then transmitted via chemical synapses to nerve cells in the brain.

Eyes of different kinds and in different insects vary widely in resolving power (detail and focus) and light sensitivity (needed ambient light) and thus in details of function.

The compound eyes are the most obvious and familiar visual organs of insects, but there are three other means by which an insect may perceive light.

Compound Eyes

The compound eye is based on the repetition of many individual units called ommatidia.

Each has a cuticular lens overlying a crystalline cone, which directs and focuses light onto 6-10 elongated retinula cells (pie pieces).

The retinula cells are clustered around the rhabdom (central vertical axis), and each contributes a rhabdomere to it. The retinula cells are surrounded by a ring of light-absorbing pigment cells, which optically isolate an ommatidium from its neighbours.

The corneal lens and crystalline cone of each ommatidium focus light onto the tip of the rhabdom. The field of view of each ommatidium differs from that of its neighbours, and together, the array of all the ommatidia provides the insect with a panoramic image of the world.

Nocturnal insects (moths), overcome this limitation with a modified optical design of compound eyes, called superposition eyes. In these, ommatidia are not isolated optically from each other by pigment cells. Instead, the retina is separated by a clear zone so that many lenses cooperate to focus light on an individual rhabdom.

Resolution generally is not as good as in apposition eyes.

Many insects have three colour-receptor types (blue, green and ultraviolet), but some insects are pentachromats. In comparison, humans are dior trichromats.

Many insects can detect the plane of polarization of light, and they utilize this in navigation, as a compass or as an indicator of water surfaces.

[ommateum]

Evolution's Witness: How Eyes Evolved

Intro

Cretaceous period approx. 145-65 million years ago.

Plants, fully established by then: flowers appeared, influencing the further expansion of animals. Invertebrates, dramatically expanded in the Jurassic, helped set the stage for the birth of insect pollinators, such as bees, beetles, and flies.

The most recent common ancestor of caddisflies (moths) was an ancient and early nocturnal insect that arose from an aquatic home, bringing superposition eyes with it.

Moths and Butterflies

Of the three forms of apposition compound eyes, butterflies are the only lineage that has the afocal configuration.

The afocal apposition eye’s crystalline lens in the proximal tip of each ommatidial cone is a second element in an extraordinary lens system. Positioned differently from that of a standard focal apposition eye, this lens permits image enlargement. In effect, the lens is a mini–magnifying telescope for each ommatidium.

But the pebbled surface of their eyes helps avoid reflection to permit greater absorption of light.

As with many other insects, butterflies also see into the ultraviolet, have colour vision, and can even detect polarized light.

Wasps, Bees, Ants, and Sawflies

Each ommatidium is set at a slightly different angle, and, much like a digital camera with pixels, the ommatidium adds its separate view to the combined visual field. The angle of each, combined with the number of ommatidia, determines the quality of the image.

In apposition eyes, the trade-off for this increased image quality is the loss of individual photon capture and, hence, overall sensitivity.

Schwab, Ivan R. Evolution’s Witness : How Eyes Evolved. New York, Oxford University Press, 2012.

[ommateum]

Evolution's Witness: How Eyes Evolved

Superposition

The superposition eyes are classified into three categories as well—refracting superposition, reflecting superposition, and parabolic superposition.

Because of their anatomy and optics, superposition eyes have much better light-gathering capabilities than apposition eyes. Animals that have colonized dimmer environments have evolved superposition eyes in response to lower light levels.

Externally, the apposition and refracting superposition eyes are similar, with hexagonal external facets. But internally, they differ greatly.

Together the two lenses essentially make a telescope.

Schwab, Ivan R. Evolution’s Witness : How Eyes Evolved. New York, Oxford University Press, 2012.

[ommateum]

Evolution's Witness: How Eyes Evolved

Apposition

The apposition eyes can be classified into three groups— true or focal apposition, afocal apposition, and neural superposition.

The horseshoe crab is one of the oldest extant arthropods. The basic compound eye, the apposition eye, had its start close to the birth of the horseshoe crabs, so their eye may be as close as we can ever get to the original apposition compound eye of the Cambrian animals.

The focal apposition compound eye consists of an array of ommatidia or “little eyes.” Each ommatidium consists of an overlying “cornea” that focuses light onto a crystalline cone (lens) surrounded by a collar of pigment cells. These pigmented collar cells prevent light and the cellular signals from spilling across to adjacent cells. The receptor cells found deeper within each ommatidium surround a central core photoreceptive element called the rhabdom.

The retinular cells compose the “photoreceptor” element (rhabdom) in a complicated manner. The rhabdom contains the visual pigment that reacts to the photons and initiates the signal sent to the brain.

The brain will assemble these units like a jigsaw puzzle or a mosaic to create an image. The array of ommatidia in an appositional compound eye produces good sensitivity to movement. But acuity can be limited by diffraction and photon capture, so this eye performs best— or perhaps only —in a daylight environment.

Schwab, Ivan R. Evolution’s Witness : How Eyes Evolved. New York, Oxford University Press, 2012.

[ommateum]

Evolution's Witness: How Eyes Evolved

Intro

Cambrian Period approx. 543– 490 million years ago.

Cambrian animals developed many of the prominent features found in modern arthropods.

The development of some form of compound eye, which most arthropods have, was a major step in the evolution of vision.

A principal difference between the simple eye and the compound eye is the number of lenses in each visual unit.

Compound eyes are found in two basic designs: apposition and superposition.

Schwab, Ivan R. Evolution’s Witness : How Eyes Evolved. New York, Oxford University Press, 2012.

[ommateum]

Encyclopædia Britannica

The compound eye, made up of a number of facets, resembles a honeycomb; each facet overlies a group of six or seven retinal cells that surround the rhabdom. Each of the retinal units below a single facet is termed an ommatidium. The number of facets varies.

During light reception, rays from a small area of the field of view fall on a single facet and are concentrated upon the rhabdom of the retinula cells below. Since each point of light differs in brightness, all the ommatidia that form the retina receive a crude mosaic of the field of view.

Each ommatidium is commonly shielded by a curtain of pigmented cells that prevent the spread of light to neighbouring ommatidia. This is called an apposition eye.

Crustaceans and insects, however, have a pair of well-developed compound eyes, each consisting of a large number of visual units called ommatidia. Each ommatidium contains six to eight sensory receptors arranged under a cornea and refractile cone and is surrounded by pigment cells, which adjust the intensity of light. Each ommatidium can act as a separate eye and is capable of responding to its own visual field. Such an arrangement seems particularly well suited for detecting movement across a wide visual field.

Wigglesworth, Vincent Brian. "insect". Encyclopedia Britannica, 7 Dec. 2024, https://www.britannica.com/animal/insect.

Erulkar, Solomon D. and Lentz, Thomas L.. "nervous system". Encyclopedia Britannica, 15 Jan. 2025, https://www.britannica.com/science/nervous-system.

[ommateum]

Oxford English Dictionary

The earliest known use of the noun ommateum is in the 1880s. OED's earliest evidence for ommateum is from 1883, in a paper by Ray Lankester, zoologist, and G. C. Bourne.

“This enlarged portion of the hypodermis is, in fact, the soft or living tissue of the eye [of the Scorpion], and may be distinguished from the lens in front of it by a special name. We propose to call it the ‘ommatéum.’ The ommateum and the lens together form the eye.”

E. Ray Lankester, and A G Bourne. “The Minute Structure of the Lateral and the Central Eyes of Scorpio and of Limulus.” Journal of Cell Science, vol. S2-23, no. 89, 1 Jan. 1883, pp. 177–212, https://doi.org/10.1242/jcs.s2-23.89.177.

[ommateum]

Etymology

First recorded between 1880–85: ommat meaning eye (stem of ómma) + eum (suffix for noun).

This word is now obsolete.

[ommateum]

Definition

Ommateum: a compound eye, as of insects, crustaceans, and other invertebrates. Comprises numerous small visual units called ommatidia (plu.: ommatea).

It is the term used to describe the entire compound eye structure in certain arthropods.

[ommateum]

1898 Webster's Dictionary

“Ommateum.” Webster’s International Dictionary of the English Language, Edited by Noah Porter Australasian, G. & C. Merriam Company, 1898, p. 1001, archive.org/details/webstersinternat00port/page/1000/mode/2up.