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PRACTICAL PROJECT 2012/2013 SCHOOL OF BIOLOGICAL SCIENCES
Can Bumblebees Distinguish Between Different Types of Iridescence?
Cordelia Batt, 1007206, cb0200@my.bristol.ac.uk
For submission to: Animal Behaviour
Supervisor: Dr Heather Whitney
Word Count: 4,691

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Iridescence, the change in hue corresponding to the viewing angle, is utilized1
by a large number of living organisms. Recently this optical phenomenon has2
been identified in the petals of many plant species, most likely as a signal to3
their specific pollinators. Bumblebees are able to distinguish iridescence from4
basic pigment colour, however there is more than one different type of5
iridescence; our experiment set out to discover if the bumblebee species,6
Bombus terrestris, can successfully discriminate between them. Our method7
involved training the bees’ to associate a certain type of iridescence with a8
reward, before adding different types of iridescence into the test environment.9
If the trained bee showed a preference towards the known, rewarding10
iridescence, it must, to a certain degree, be able to distinguish between them.11
We found that in most cases, this was true and bees were more likely to visit12
the known, rewarding iridescence. This infers that bees could be using not13
only pigment colour, but also structural colour to select rewarding plant14
species in their environment. Iridescence may therefore play an important role15
in improving foraging efficiency in bees.16
KEY WORDS17
Pollinator; pigment colour; structural colour; iridescence; multilayer;18
diffraction grating; colour constancy.19
20
The mutual relationship between plants and their pollinators is constantly evolving so21
that plants are more conspicuous to their pollinators. Similarly pollinators have22
become better equipped to receive visual signals from plants, which due to their lack23
of mobility often rely on insects for sexual reproduction. For this reason, plants24
display bright flowers, the colours produced by reflecting certain specific wavelengths25
of light which are perceptible to their pollinators. Colours can be produced by26

3. 3
chemical pigments, or specific surface structures. Pigment colours are produced by27
chemicals which absorb most of the visible light spectrum; the wavelengths not28
absorbed determine the perceived colour of the object. Structural colours are those29
produced by means other than pigments, where certain light wavelengths of light are30
selectively reflected from a surface. The resulting colours are often more intense than31
those produced by pigment colours (Glover & Whitney, 2010).32
Structural colour has been recognised in nature for a long time, most notably in33
birds, insects and fish, however many reptiles and amphibians are also iridescent.34
The purpose of iridescence in many of these organisms includes species and sex35
recognition, as well mate choice and predator deterrence (Doucet & Meadows,36
2009). Recent studies have shown that many plant species also exhibit iridescence.37
Much of the iridescence occurs in the ultraviolet (UV) wavelengths, and unlike us,38
these signals are recognized by bumblebees, whose’ visual systems have high acuity39
in the blue and near-UV ranges (Whitney et al., 2009). Iridescence, like many other40
visual cues such as pigment colour (Gumbert, 2000), fluorescence (Gandía-Herrero,41
García-Carmona & Josefa Escribano, 2005) and patterns (Whitney, Kolle, Alvarez-42
Fernandez, Steiner & Glover, 2009), is thought to be used by plants as a means to43
attract pollinators. Bumblebees can not only detect iridescence independently of44
pigment colour (Whitney et al., 2009), but they are also more attracted to flowers that45
display it (Glover & Martin, 2002). This suggests an evolutionary advantage to46
structural colour in plants with regard to insect pollination. Any increase in the47
efficiency of pollination is not only relevant to ecosystems, but also to global food48
production, which relies heavily on insect pollination.49
There is no single means of producing iridescence. Diffraction gratings, multilayers50
and photic crystals are all mechanisms that produce structural colour (Glover &51
Whitney, 2010), allowing a variation in the optical properties of plants. Bumblebees52
are very specific in the flowers that they visit, each species favouring certain plant53

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types (Goulson, 2013). It could therefore benefit bumblebees to be able to use these54
differences in iridescence to categorise particularly favourable plant species. We55
know that bumblebees can distinguish iridescence from simple pigment colour, but56
can they recognise the slight differences in structural colour produced by flowers of57
different species? More simply, can bumblebees discriminate between different58
iridescences? We tested to see if naïve bumblebees, Bombus terrestris, were able to59
discriminate between certain types of iridescence by using different mechanisms60
including diffraction gratings and multilayers to produce structural colour. If the bees61
could learn to categorise the different structural colours depending on whether or not62
they offered a reward, then we can conclude they are able to distinguish between the63
different kinds of iridescence.64
65
METHODS66
General Setup67
Bombus terrestris colonies were set up in a cardboard nest box which was attached68
to a glass flight arena 110cm in length, 70cm wide and 100cm high. The bees could69
enter the flight arena via a transparent pipe in which plastic partitions could be70
added, allowing the successful selection of a single bee. The lighting in the laboratory71
comprised six Sylvania Activa 172 Professional 36W fluorescent tubes.72
The bees were naïve with respect to foraging from natural flowers, and hadn’t been73
used for any previous experiments. They received half a pcr plate filled with a 30%74
sucrose solution daily. Over the weekend a gravity feeder was provided, filled with a75
solution mimicking that of the bees’ natural diet (Provided by Koppert Biological76
Systems, who also provided the bees.) Pollen was added to the colony on a weekly77
basis.78

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How the Targets were Produced79
Targets were provided by Dr Heather Whitney, they were produced by adding80
different surfaces to artificial flowers constructed from Sterilin tubes 26mm diameter81
and 8cm high, with an inverted white lid 70mm diameter on top. The surfaces were82
circular plastic discs, with a diameter of 40mm. The inverted lid of a 0.5 ml Eppendorf83
tube placed in the middle of the target to contain the sucrose reward.84
There were 5 different target types categorised by the surface type on the lid. Two85
were non-iridescent; gloss a smooth moulded plastic and matt rough moulded plastic.86
Three of the targets were iridescent. Two of these were created using diffraction87
gratings; one being artificially produced using ordered rows of grooves on the88
surface; the other was other created using a mould of the adaxial petal surface89
whereby the grooves where much more variable. The third kind of iridescence was90
multilayer iridescence; thin films of optical material arranged in ordered layers. The91
targets were all maintained at room temperature. For ease I will refer to gloss surface92
as gloss; matt surface as matt; diffraction grating iridescence (artificial) as artificial;93
diffraction grating iridescence (natural) as floral and multilayer iridescence as94
multilayer.95
Marking the Bees96
The bees were distinguished using paint marks on their thorax. These were applied97
using a wooden skewer when the bees’ concentration was diverted by sucrose98
solution. We used between 1 and 4 dots of varying sizes and shapes (circles and99
lines for example) using the 5 different colours available to us. This enabled us to100
differentiate between large numbers of bees.101
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Control Tests104
Before the test the bees were hungry having not been fed since the previous day.105
The test arena was cleared of all artificial flowers and any foraging bees, which were106
either encouraged back into the hive or captured under Sterilin tubes.107
Targets were placed randomly within the test arena. There were 3 of each kind of108
target, so 15 in total. They were free of any reward. Before starting the control we109
defined a ‘land’ to constitute of all 6 legs placed on the target. We used the same110
observer for all the tests to eliminate any potential differences in classification of a111
‘land.’112
One bee was released at a time. We allowed 20 lands, recording which targets113
were landed on. Once 20 lands were completed sucrose solution was added to the114
target the bee was situated on, and the bee was allowed to drink and return to the115
hive.116
The targets were removed, washed and cleansed with ethanol so that any remaining117
traces of sucrose were removed. Equally any signals that previous bees could be118
leaving would also be removed. The targets were then replaced and repositioned,119
and the experimental procedure repeated for a time with a different bee. A total of 20120
bees were tested.121
Training to Iridescence122
Firstly, we trained bees to multilayer iridescence. The test arena was cleared of any123
bees and 3 targets with multilayer iridescence were randomly placed inside. Each124
target had an approximately 1ml reward of 30% sucrose solution, which was refilled125
up once emptied. We tested one bee at a time allowing it to drink 20 times from any126
of the 3 targets before commencing with the experiment.127

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All the multilayer targets were then removed, washed and cleansed with ethanol.128
They were returned to the test arena along with 3 of each of the other types of target,129
making a total of 15 targets. None of the targets had a reward. The trained bee was130
released, and we recorded which targets it landed on. A total of 20 bees were trained131
to multilayer and tested. This procedure was repeated to train the bees to floral.132
Different bees were used for each trial.133
We moved onto a second hive to train the bees to artificial. We completed a control134
test for this hive before obtaining results and used the same methods as previously135
described.136
137
Statistical Analysis138
We used a Chi squared X squared test to analyse the control, to see if the bee visited139
a certain kind of target more frequently than expected by chance. If yes, it would140
indicate that the bees have an innate preference to a certain target.141
We also used the Chi squared test when analysing our results with trained bees.142
This allowed us to see if after training, the bee visited a certain type of iridescence143
more times than expected by chance.144
145
RESULTS146
Control Experiments147
The control for hive 1 showed that there was no innate preference for a certain type148
of iridescence (Chi-square test: X10 = 8.55, P = 0.0734). This was also true for hive 2149
(Chi-square test: X10 = 3.95, P = 0.413).150
151
Results After Training152
After being trained to multilayer, the proportion of visits each bee made to the153
multilayer target increased significantly compared to the control (Chi-square test: X20154

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= 111, P <0.001; Figure 1). This was also the case after training the bees to floral155
(Chi-square test: X20 = 56, P <0.001; Figure 1).156
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Figure 1166
Proportion of bees visiting each type of iridescence during the control, after training167
to multilayer and after training to floral.168
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Training to artificial did not significantly increase the number of visits the bees made170
to the artificial disc compared to the other disc types (Chi-square test: X20 = 4, P =171
0.406).172
173
Extra Analysis174
Matt175
We noticed the bees visited matt very infrequently during our test experiments. We176
tested the significance of this and indeed the bees did visit matt less than any of the177
other targets after training (Chi-square test: X80 = 38.58, P <0.001; Table 1).178
Secondary Preferences179

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We looked to see if the bees showed any obvious secondary preferences. After180
training to floral and multilayer, the bees’ preferentially visited the target they were181
trained to, but gloss was the second preference (Table 1; Figure 2; Figure 3).182
We also noticed that the bee visited multilayer and gloss a similar number of times in183
each experiment. This is evident from Table 1.184
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186
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Table 1 The visits made to each target type when trained to multilayer, floral and188
artificial iridescences, ordered from the highest to the lowest number of visits. The189
number of visits made to multilayer and gloss have been highlighted in red.190
Trained to
multilayer
Multilayer Gloss Floral Artificial Matt
No. of visits 160 82 65 51 42
Trained to
floral
Floral Gloss Multilayer Artificial Matt
No. of visits 130 91 69 67 41
Trained to
Artificial
Artificial Floral Gloss Multilayer Matt
No. of visits 93 82 81 75 69

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Figure 2202
The number of visits made by the bee to each target type after training to the203
multilayer target had taken place.204
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Figure 3216
The number of visits made by the bee to each target type after training to the floral217
target had taken place.218

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219
Spatial Distribution220
We noticed that the spatial distribution of the targets had an effect on the first target221
visited by the bee. The nearest target to the hive was often the first landed on. This222
prompted us to record which target was nearest, before seeing if the proportion of223
visits made by bees on their first landing to this particular target was higher than224
expected by chance. In most instances this was the case. When the multilayer target225
was nearest the hive exit, the bees’ primary landing was mostly on the multilayer226
target (Chi-square test: X14 = 24.57, P < 0.001). This was also the case for matt227
(Chi-square test: X21 = 30.7, P = <0.001), floral (Chi-square test: X15 = 16, P =228
0.03), and gloss (Chi-square test: X16 = 18.4, P = 0.001). The result when the229
artificial target was nearest the hive was non-significant (Chi-square test: X14 = 5.29,230
P = 0.259).231
232
DISCUSSION233
Our results show that bumblebees visit multilayer iridescence more often compared234
to other iridescences once a reward association had been learnt. The same is true235
for floral iridescence. This suggests that bees can discriminate between different236
types of iridescence and may use this information to improve foraging efficiency.237
238
Iridescence in Nature239
Colour in nature can be produced by chemical pigments or surface structures.240
Pigment colour is the complementary colour that remains after all other wavelengths241
have been removed by a chemical pigment. Structural colour occurs when an objects242
surface reflects certain wavelengths of light, thus producing an iridescent effect243
(Glover & Whitney, 2010). Iridescence, from the Greek ‘iris’ meaning rainbow, can be244
described as a change in colour depending on viewing geometry (Meadows et al.,245
2009). Despite only being reproduced by humans relatively recently, iridescence has246

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been present in nature for millions of years. Recent research has suggested that247
many of the shells of animals from the Burgess Shale, British Columbia, where in fact248
iridescent. These animals are thought to have lived around 515 million years ago in249
the Cambrian period, a time of rapid evolutionary change. The evolution of250
iridescence, alongside that of more advanced visual systems capable of detecting251
structural colour, may have played a role in this explosion of metazoan evolution.252
Iridescence is seen in a broad range of taxa in nature, from algae to birds of253
paradise. Some examples of its uses are mate recognition in Helioconius butterflies254
(Sweeney, Jiggins & Johnsen, 2003), seed dispersal in Elaeopcarpus trees (Lee,255
1991) and indications of quality in many bird species (Fitzpatrick, 1998).256
There are different ways in which plants and animals can produce iridescence. The257
most common seen in nature are diffraction gratings and multilayers. Diffraction258
grating iridescence is produced by grooves or depressions on a surface that disperse259
different wavelengths of light in different directions. A wide range of arthropods make260
use of diffraction gratings. It was first noticed in scarab beetles, Serica serica (Seago,261
Brady, Vigneron & Schultz, 2009) and has later been noted in many other species,262
including the spider Cosmophasis thalassina (Parker & Hegedus, 2003). Multilayer263
iridescence is caused by the layering of optical materials; but again light is reflected264
differently depending on its wavelength. A striking example of multilayer iridescence265
in nature is that of the Morpho butterfly. The vivid blue colouration of its wings can be266
seen from great distances despite them containing no blue pigments (Glover &267
Whitney, 2010).268
Structural colours are often brighter than pigment colours; this is because they are269
more specific in the bandwidths they reflect. Pigment colours reflect a broader270
spectrum of light, which contains a mixture of colours, resulting in a less intense271
colour (Glover & Whitney, 2010). Photic crystals are another, less common way of272
producing structural colour. This kind of iridescence is produced by a tetrahedral273
microstructure that diffracts light at different angles, reflecting bright colour over a274

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broad angle. Photic crystals are seen in the butterfly species Parides sesostris275
(Vukusic & Sambles, 2003).276
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Plant Use of Iridescence278
Around 100 million years ago, a mutualistic relationship between plants and insects279
was developing. In the early stages insects seeking protein rich pollen had to find280
brown or green flowers amongst the foliage. It wasn’t long before more conspicuous281
flowers evolved, attracting more insects and increasing the efficiency of insect282
pollination. Water lilies and magnolias were the first plants to evolve petals; they283
were white and conspicuous against the dull background (Goulson, 2013.)284
Fluorescence, contrasting colour patterns, and we now think iridescence evolved in285
some plants to further advertise their position to pollinators. Often more than one286
pollination signal is compiled, creating an even stronger basis for discrimination. For287
example Hibiscus trionum has a dark base on each of its petals produced by purple288
pigmentation. This presumably acts like a target, guiding the pollinator to the nectar289
reward. This guide is made even more eye-catching to the bee by the presence of an290
overlying iridescence (Whitney, Kolle & Alvarez-Fernandez et al., 2009).291
Iridescence is utilised by plants for diverse reasons, including predation avoidance,292
defence against high light levels, fruit dispersal and even non-communicational roles293
such as integument strengthening and water repellence (Doucet & Meadows, 2009).294
Multilayer iridescence can sometimes be seen in the leaves of plants which inhabit295
shaded areas, where it is thought to increase the absorption of wavelengths more296
abundant in this low light environment. For example-species in the genus Selaginella297
exhibit iridescence when growing in the shade, but not when growing in more direct298
light (Hébant & Lee, 1984).299
More recently, diffraction gratings have been shown in petals of plant species300
including Tulipa humilis, Hibiscus trionum and Mentzelia lindleyi. Although not visible301
to the human eye, the cuticular striations seen from a scanning electron microscope302

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enable scientists to infer iridescence in the UV spectrum. This iridescence, which303
although invisible to the human eye, is very obvious to bees, is likely to be used in304
the attraction of pollinators. In some plants iridescence is used to aid mimicry. For305
example iridescence on an enlarged petal known as the labellum in the306
pseudocopulatory orchid Ophrys, helps with the deception of male wasps and solitary307
bees. They are tricked into thinking that the labellum is the iridescent female of their308
species (Whitney, Kolle & Alvarez-Fernandez et al., 2009). So far 10 angiosperm309
families have been identified to contain at least one species with iridescent petals.310
Bearing in mind that over 50% of angiosperms exhibit a textured petal surface, it is311
highly likely that a much higher number of flowers than currently described are312
iridescent (Whitney, Kolle, Andrew et al., 2009).313
314
Bumblebee Foraging Behaviour315
Bumblebees, like their relatives the honey bees, feed on the nectar and pollen316
produced by many plants. This process results in the pollination of a vast proportion317
of many fruit and vegetable crops globally. Therefore it is extremely important not just318
regarding ecosystem functioning, but also to the economy and food industry. There319
are over 250 species of bumblebee, mostly present in the northern latitudes, each320
species favour certain flower types. Specialised anatomy helps them to exploit their321
preferred species, for example the garden bumblebees, Bombus hortorum, are one322
of the few species with a tongue long enough to reach the nectar in foxgloves323
(Goulson, 2013). Bumblebees are highly reliant on visual cues to find specific flower324
species, and hence have evolved highly sensitive compound eyes made up of many325
ommatidia.326
Bumblebees are trichromatic; their 3 photoreceptors produce sensitivity peaks in the327
UV, blue and green regions of the visual spectrum (Skorupski, Döring & Chittka,328
2007). Slight sensitivity differences in the photoreceptors of different species have329
fine-tuned bumblebee colour vision towards their preferred plant species, improving330

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foraging efficiency (Chittka & Menzel, 1992). The fact that visual cues are so331
important in flower identification is reflected by the fact that mainly the larger bees,332
which have increased visual capacity, forage for the hive (Goulson, 2013). Evidence333
that bumblebees can distinguish structural colour was provided in experiments where334
bumblebees where trained to targets displaying artificial iridescence. The bees’ were335
later capable of correctly identifying and choosing this target type over non-iridescent336
targets displaying the same pigment colour. This shows that bees’ can successfully337
distinguish structural colour from pigment colour. The bees’ could also distinguish the338
more variable floral iridescence, which would be present in nature (Whitney, Kolle,339
Andrew et al., 2009).340
Bumblebee flower choice reflects innate preferences as well as learnt associations341
between certain colours and a reward (Gumbert, 2000). Although naive bumblebees342
showed no preference towards structural colour in our experiments, they successfully343
learnt associations between certain iridescences and a reward. Alongside innate and344
acquired preferences towards certain pigment colours, this ability to discriminate345
between different structural colours could offer bees’ a powerful means to categorise346
different flowers in their environment. Experiments on wild populations of Antirrhinum347
majus show that this may be the case. A mutant line of these flowers lacking348
iridescence were visited significantly less than their iridescent counterparts by bee349
pollinators (Glover & Martin, 2002).350
Our results showed that as well as distinguishing iridescence from pigment colour,351
bees could also discriminate between different kinds of iridescence. This was true for352
floral and multilayer iridescence (Figure 1); unfortunately our results when training to353
artificial iridescence were non-significant. This is contrary to what we expected, and354
previous findings by other researchers. This contradictory result may have been355
caused by experimental procedure; we could have used a larger sample of bees356
thereby increasing the significance of our results. We could also have increased the357
effectiveness of our training method by using differential conditioning as opposed to358

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operant conditioning. This would involve the use of a quinine forfeit for when the bee359
selected an incorrect target type. It has been proved that differential conditioning360
does in fact improve bees’ ability to discriminate between different colours (Dyer &361
Chittka, 2004). There was also a clear difference in the hive quality. Our training to362
artificial commenced in a second hive, where the bees were acting irrationally, not363
returning to the hive from the test arena, so it is possible the queen had lost control of364
her workers.365
The significance of our results could have been improved with respect to spatial366
design. As noted in the results section, bees had a tendency to land on the nearest367
target. This is likely because naïve bumblebee foragers use movement rules when368
foraging. These involve short movements to begin with; therefore it is likely that the369
bees’ first land will be on the closest target (Burns & Thomson 2005). Furthermore370
with respect to spatial distribution, assigning coordinates to the test arena and using371
a random number generator to determine the target positions in each test would have372
removed any bias. Despite thinking that we were placing the targets randomly,373
there’s a possibility that we may have been subconsciously placing them in certain374
areas. Bumblebees have extremely good spatial memory, so if we had been placing375
the targets non-randomly, this could have affected our results.376
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The Blue Tulip Colour Hexagon387
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Figure 4: The Blue Tulip Colour Hexagon402
A plot of photoreceptor excitation for the trichromatic colour vision system of Bombus403
terrestris. The points represent the level of stimulation each photoreceptor (UV, Blue404
and Green) incurs whilst the viewing angle of each surface was altered (Whitney &405
Sandbach, unpublished). As the distance between 2 points increases, so does the406
bees’ ability to discriminate between the 2 surfaces (Chittka, 1992).407
The Bee Colour Hexagon (Figure 4) has been created with respect to the different408
target types used in our experiment. From this particular model we can infer, how409
easy or difficult it is for the bee to distinguish between matt, gloss, multilayer, artificial410
and floral surfaces. For the iridescent targets there is quite a large spread of points411
across the visual spectrum due to the reflection of a multitude of different412
wavelengths by the iridescent surface depending on the angle of approach. This413

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causes the excitement of a larger number of photoreceptors and is why iridescent414
surfaces appear different depending on the angle of approach. This could have415
negatively affected the bees’ ability to learn the iridescent targets; however this didn’t416
seem to be the case. Perhaps the bees have a mechanism allowing them to417
compensate for this visual phenomenon. A colour constancy mechanism is seen in418
the honeybee with regards to pigment colour when illumination changes (Faruq,419
Mcowan & Chittka, 2013), and it is reasonable to assume that a similar mechanism420
allows bees to categorise structural colour, despite the changes in spectral421
reflectance with viewing geometry. The mechanisms involved in helping the bee to422
categorise different structural colours are as yet unknown. Adaptation of423
photoreceptors could play a key role, or higher input may be needed, from the central424
nervous system for instance.425
The non-iridescent targets, matt and gloss, occupy much smaller areas on the426
visual spectrum, as very little scattering of light occurs on reflection. A small amount427
of scattering occurs when light hits the matt target due to specular reflection,428
whereby small reflective facets dispersed randomly on the surface cause a small429
amount of light scattering (Torrance & Sparrow, 1967). It could be assumed that the430
smaller range of the non-iridescent targets may increase the ease of discrimination431
for bees. This seems to be true for matt, which the bees visit less often once trained432
to the iridescent targets; showing that they can readily distinguish it as non-rewarding433
(Table 1). However gloss also has a small range, but is still visited at a high434
frequency, similar to multilayer (Figure 2; Table 1) which has a much larger range.435
The fact that gloss and multilayer are visited at similar frequencies is interesting, as436
they occupy similar areas in the bees’ visual spectrum (Figure 3), meaning they437
excite a similar repertoire of photoreceptors. This suggests an overlap of visual438
ranges may make it harder for bees to distinguish between different surfaces.439

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The different surfaces used in the experiment where added to a white lid leaving a440
visible rim around the perimeter of the target. This may be significant as bees are441
often attracted to contrasting colours when foraging (Lunau, Wacht & Chittka, 1996).442
We do not know the spectral properties of the white lid, however if it contrasted more443
greatly with certain surfaces used in our test, this may have increased its attraction to444
the bees and could have affected our results.445
446
Conclusion447
Our experiments and previous research conclude that bumblebees’ can successfully448
distinguish different kinds of iridescence from simple pigment colour, and each other.449
They achieve this despite the significant changes in appearance produced by450
different viewing angles and changes in the spectral composition of the illuminant.451
Ecological studies of bumblebees have shown that they usually exhibit constancy in452
the flowers that they visit, often detecting favorable species using visual signals.453
Categorising flowers using differences in their structural colour as well as pigment454
colour is likely to improve the foraging efficiency of bumblebees, thereby increasing455
their chances of survival.456
It would be interesting to find out exactly how important structural colour is in457
comparison to other more widely known visual cues. Bearing in mind the importance458
of bumblebee pollination to the economy, even a slight advantage incurred by the459
use of structural colour could have huge implications to not just bumblebee460
populations, but also the human race. It is also important to know whether the461
bumblebee’s ability to categorise colour is altered by changes in the light462
environment. If so, this could be relevant in areas affected by smog and other463
anthropogenic pollutants which may reduce the efficiency of pollination, ultimately464
affecting the survival chances of the hive. In a time when bee diversity has declined465

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markedly, any information concerning their ecology could be used to aid bumblebee466
conservation, and hopefully reverse this decline.467
468
ACKNOWLEDGEMENTS469
Thanks are due to my supervisor Dr Heather Whitney, who provided valuable470
information on laboratory conduct when working with bumblebees’ and helped us471
greatly with our experimental procedure. Also thanks to Lucy Sandbach who472
provided us with the bee colour hexagon and was available to answer any queries on473
its production. A final thanks to my project partner, without whom I couldn’t have474
carried out any of the experiments.475
476
REFERENCES477
478
 Burns,J.G., & Thomson, J.D. (2005). A test of spatial memory and movement479
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Ecology, 17, 48-55481
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 Chittka,L,. & Menzel, R. (1992). The evolutionary adaptation of flower colours483
and the insect pollinators’ colour vision. Journal of Comparative Physiology A,484
171, 171-181485
 Doucet, S.M., & Meadows, M.G. (2009). Iridescence: a functional perspective.486
Journal of the Royal Society, 6, 115-132487
 Dyer, A.G., & Chittka, L. (2004). Fine colour discrimination requires488
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