A hive moved
just a short distance will create difficulties for foraging honey bees
returning home, which makes one question the visual ability of bees. Honey bee
vision differs from vertebrate species in many ways, such as the speed of image
detection and seeing certain colors and light, but their ultimate visual
interpretation has similarities (Horridge 2009). When relocating their hive,
honey bees depend on the sun’s relative location as a visual cue. Other dynamic cues, such as plant life during
the foraging season, are inconsistent and therefore may make hive recognition
difficult (Borst 2018). Therefore, the appearance of sunlight is a more
reliable navigational signal than the bee’s memory of the hives location.
Read on to
learn more about…
A Honey Bee’s Perspective: Sight
Honey bees
have three small eyes in the top-center of their head, called ocelli, and two
large eyes on the side of their head, called compound eyes (Riddle 2016).
Ocelli have single lenses and help the bee maintain stability and navigation, using
light intensity and spatial orientation (Riddle 2016). The compound eyes
contain numerous simple eyes, called ommatidia, which are arranged together to
form a hexagonal pattern (Horridge 2009). There are approximately 6,900 facets
in worker bee eyes and 8,600 facets in drone bee eyes (Riddle 2016). Behind
each hexagonal facet there are eight photoreceptors, detecting variations in
light intensity (Rigosi et al. 2017).
Honey bees
can use celestial cues to determine their spatial position. Their eyes can
detect polarized light and match polarization patterns in the sky to use as a
navigational system, which is what bees use for the ‘waggle dance’ (Riddle
2016). Polarized light is sunlight that is sent in one direction after
travelling through the atmosphere and can be seen by the bees even on cloudy
days (Borst 2018). Bees can also easily distinguish between dark and light, making
them very good at seeing the edges of objects, but they can have trouble
between similar shapes that have smooth lines, such as circles and ovals
(Shipman, 2011).
Like humans,
honey bees are color trichromats, meaning they have three classes of photoreceptors
maximally sensitive in three regions of the electromagnetic spectrum (Dyer et
al. 2008). When comparing the function of each type of photoreceptor, the
respective wavelengths are measured in units called nanometers or nm. The types
of photoreceptors are S (short wavelength type) with an absorption peak at 344
nm (ultraviolet), M (medium wavelength type) with an absorption peak at 436 nm
(blue), and L (large wavelength type) with an absorption peak at 544 nm (green)
(Avargues-Weber et al. 2012). Therefore, honey bees can see roughly 300 to 650nm
and humans can see 390 to 750nm on the electromagnetic spectrum, which means
bees can see ultraviolet, but not red (Shipman 2011).
Resolution
is maximized in the frontal part of honey bee’s eyes, meaning that their focus
is fixed. The visual angle indicates the size of object which can be seen by
the bee. This angle, measured in
degrees, is the distance between imaginary lines drawn from the focal point of
the eye to the extreme edges of the object being visualized. So, a small or distant object will
have a low visual angle and a large or near object will have a high visual
angle. Honey bees can clearly see an
image that is as small as 1.9 degrees, which is approximately the width of a
person’s thumb at arm’s length. The smallest object a bee can detect, although
not clearly, is 0.6 degrees (Rigosi et al. 2017). Although relatively poor at seeing
detail, when compared to vertebrates, bees are very good at detecting
movement. They can visualize movements
that happen at 1/300th of a second, whereas humans can only detect at 1/50th of
a second. So, honey bees may not be able to see as far as most vertebrate
species but while flying, they can detect images much faster.
Some people
assume that honey bees observe the world the same way humans do, but the bee’s
eye has adapted to help the bee to be an efficient forager of flowers. While
bees are flying at an average speed of over 20km/h, they need to be able to
identify small flowers, predators, and their hives among vegetation. Honey bee
eyes can do this due to their ability to detect certain types of light and the
speed of image detection.
Connecting with ATTTA Specialists
References:
Avargues-Weber
A, Mota T, Giurfa M. 2012. New vistas on honey bee vision. Apidologie
43:244-268.
Borst P.
2018. What do bees see? Bee Culture: The Magazine of American Beekeeping.
Dyer A,
Spaethe J, Sabina P. 2008. Comparative psychophysics of bumblebee and honeybee
colour discrimination and object detection. Journal of Comparative Physiology
194:617-627.
Horridge A.
2009. What does a honeybee see? And how do we know?: A critique of scientific
reason. Chapter 5: The retina, sensitivity, and resolution. 85-116.
Riddle S.
2016. How bees see and why it matters. Bee Culture: The Magazine of American
Beekeeping.
Rigosi E, Wiederman
S, O’Carroll D. 2017. Visual acuity of the honey bee retina and the limits for
feature detection. Scientific Reports 7:45972.
Shipman M.
2011. What do bees see? And how do we know? NC State University.