I've had a great time reading the colour vision thread. The large amount of
interest in bee vision is likely because humans rely so heavily on sight.
Bees, I think, are far more concerned about 'smelling'. But, bee sight is
very important to understand. Bees need vision for foraging, mating and
finding home.

I took some time today in the library to read a few recent(ish) journal
items. Much of the detailed scientific work is highly technical and I
sometimes found it difficult to interpret. Especially because insect
physiology is well outside my area (autogenous biologics). I won't bore you
with the nitty gritty. The good news is the significant findings are
straightforward.

Bee sight relies on a photon gathering and interpretation system using a
compound eye. Each compound eye of workers consists of approximately 4500
facets, queens 3500 facets and drones a whopping 7500. Each facet embraces a
very tiny field of view. Every individual facet is analogous to a retina,
albeit very small. The main purpose is photon capture. The brain receives a
nerve impulse from the receptor cells in the ommatidium after captured
photons cause a chemical change when absorbed. Each ommatidium has nine
receptor types biochemically specialized for 'colour'. Four are 'green'
receptors, two are 'blue' receptors, two for 'UV" and one for polarized UV.
Some investigators seem to disregard a specialized 'Polaroid' UV receptor
and simply consider eight receptor types. The brain assembles, from the
generated nerve impulses, the 'picture' that is bee sight. The bee seems to
'see' UV and all the colours we do except red (a bee's black). The prevalent
conceptualization of the 'picture' the bee sees is a distorted mosaic. A
notion very familiar to everyone on this list.

I am not convinced the bee perceives a mosaic at all. Just what the bee
'perceives' is still little understood. The concept of mosaic vision is no
doubt excellent for understanding the underlying biology of bee sight but it
lacks completeness. We lack investigations that integrate static sight with
kinematic sight. Detecting motion is very highly developed in bees. I think
what bees 'perceive' as opposed to 'see' is based on a 'visual flow' rather
than the all too human preference for static landscapes.

Giurfa et al. (1999) found that bee sight shows a marked regionalization of
colour detection that they think is a result of peripheral or central
specializations within the compound eye. Bees detect colour presented
directly in front of their eyes in visual angles greater than 15 degrees
(chromatic system). At smaller view angles between 5 degrees and 15 degrees
the bees switch to a colour-blind system (achromatic system) dependent on
the abundant 'green' receptors. (Note: targets present smaller and smaller
angular sizes the further away you get.)

The achromatic and chromatic systems work together in sequence (Hempel de
Ibarra et al., 2001). The two systems are 'tuned' to work together as visual
targets change with respect to the size of the visual angle. The dual system
means bees see solid colours better than colours within colours. Bees need a
sharp contrast and a 'fixation' point to activate their colour
discrimination at visual angles less than 15 degrees (Hempel de Ibarra et
al., 2001). Bees are unable to detect an *isolated* coloured patch that
subtends fields of less than 15 degrees without a fixation point and sharp
contrast.

Bees are colour-blind when they detect edges (Horridge 1999). Edge
perception is engaged when the most abundant receptor types (green) detect a
contrast. Because only one receptor type (green) is used, the edge detection
is colour-blind (achromatic). Now, consider kinematic vision. A detectable
moving target is a contrasting edge that moves across a visual field. I
think this means kinematic sight is colour-blind because seeing the moving
'edge' need only use the green receptors and there is no sight fixation.
This is likely the case at least for motion in the horizontal plane. The
vertical plane appears to use green and blue receptors (Horridge, 2000).
This leads to the oddest notion that bees may be colour blind in the
horizontal but may have colour vision mostly in the vertical. While flying,
it is the horizontal plane that is important in terms of 'heading' along a
route. And yes, the bee at all times is aware of its position relative to
the sun, likely using polarized UV. The vertical (up/down) plane becomes
important when working blooms at the source plant where colour perception is
put to best use.

The achromatic and chromatic systems are separated neurologically. The
'wiring' is independent but the information is used sequentially. The dual
system is an integration of a chromatic 'green and blue' processing that
disregards contrasts and achromatic 'green' edge detecting system that
disregards the *relative* location of edges but 'sees' contrast. The edge
contrast detection is only green based in the horizontal but green or blue
in the vertical (Horridge, 2000). Bees will remember the colour that was
placed in a specific position. Coloured patterns and positions are 'seen' by
combining photon flux from green and blue receptors.  The luminosity is not
important but the wavelength of the photon is.

I'll speculate a bit and suggest bees in flight may establish a route memory
based on the 'edges' that flow past its horizontal peripheral visual field.
This is the heading space. There is evidence for this, most notably in the
work of Dyer (1991) which appears to refute the 'cognitive map' idea from
Gould (1986). Horridge (1999) showed that bees can learn edge cues but it is
not likely they 'memorize' entire patterns. So I don't think bees hold
entire 'cognitive maps' in their wee bee brains. They may remember the
'termophores' (coined here first (I think)! from the Greek terma = edge and
aphoros = bearing) and their sequence but not the whole visual landscape en
route. Perhaps these termophores (edge cues) form part of the learned route
to nectar and pollen resources and back again to the hive relative to the
sun. Other sensory information such as odour accretion on the bee's body en
route; and data from propriomotic, barometric and hydrotropic organs likely
are used, too, I bet.

Perhaps the best 'bee-con' for a hive will reflect (or emit) UV, wiggle a
little bit, have a solid human perceived colour (or be black (red) and
white), be BIG, have a very obvious fixation point and lots of sequential
termophores *Burma-Shave* style along the bee line. Scented candles, too?
Hmmm.

Now where did I put that NSERC grant application.....?

Richard Goetze

Dyer FC (1991) Bees acquire route-based memories but not cognitive maps in a
familiar landscape. Animal Behavior 41:239

Giurfa M; Zaccardi G; Vorobyev M (1999) How bees detect coloured targets
using different regions of their compound eyes. J Comp Physiol A 185: 591

Gould JL (1986) The locale map of honey bees: do insects have cognitive
maps? Science 232:861

Hampel de Ibarra N; Giurfa M; Vorobyev M (2001) Detection of colour patterns
by honeybees through chromatic and achromatic cues.  J Comp Physiol A
187:215.

Horridge GA (1999) Pattern discrimination by the honeybee (Apis mellifera)
is colour blind for radial/tangential cues. J Comp Physiol A 184:413.

Horridge GA (2000) Pattern Vision of the Honeybee (Apis mellifera) blue  and
green receptors in the discrimination of translocation. Neurobiology of
Learning and Memory 74:1

The whale
Put Jonah
Down the hatch
But coughed him up
Because he scratched
Burma-Shave