About
The Beetles Project is a student-led science research project started at the Simon Langton Grammar School for Boys in 2013, where we study structural colour, such as iridescence, in beetles. As the elytra (wing cases) of beetles are easy to work with, we focus our investigations on elytra.
What is iridescence?
Iridescence is the property of surfaces that appear to change colour as you view them from different angles, whilst there is a constant angle of illumination. The Chrysochroa wallacei pictured above is an example of iridescence in animals.
What causes iridescence in beetles?
There are three main types of structure that cause iridescence in beetles; multilayer reflectors, diffraction gratings, and three-dimensional photonic crystals. As multilayer reflectors are the most abundant, we focus on them. This structure consists of two repeating translucent layers with different refractive indices, and the thickness of these layers is about a quarter of the wavelength of visible light (Figure 1, Seago et al 2009). This multilayer structure causes different wavelengths of light (i.e. colours) to reflect and refract at different angles, so different wavelengths of light will be present at different angles. These waves will interfere with each other, either constructively or destructively (Figure 2 and 3, Vibration Training), meaning that there is an increase or decrease in the intensity of the waves. Constructive interference causes certain wavelengths of light to be more abundant, and destructive interference causes other wavelengths to be less abundant. At different angles of view, the paths that rays of light travel within this multilayer reflector change, and these changes in path length cause a change in interference of the waves. This change in interference causes certain wavelengths of light to constructively interfere more when the angle of view is greater, and this leads to iridescence. In beetles, the multilayer reflectors usually contain chitin, a translucent polysaccharide similar in structure to cellulose, in at least one of the repeating layer, and the C. wallacei beetle shown above has air and chitin as its alternating layers.
What is iridescence?
Iridescence is the property of surfaces that appear to change colour as you view them from different angles, whilst there is a constant angle of illumination. The Chrysochroa wallacei pictured above is an example of iridescence in animals.
What causes iridescence in beetles?
There are three main types of structure that cause iridescence in beetles; multilayer reflectors, diffraction gratings, and three-dimensional photonic crystals. As multilayer reflectors are the most abundant, we focus on them. This structure consists of two repeating translucent layers with different refractive indices, and the thickness of these layers is about a quarter of the wavelength of visible light (Figure 1, Seago et al 2009). This multilayer structure causes different wavelengths of light (i.e. colours) to reflect and refract at different angles, so different wavelengths of light will be present at different angles. These waves will interfere with each other, either constructively or destructively (Figure 2 and 3, Vibration Training), meaning that there is an increase or decrease in the intensity of the waves. Constructive interference causes certain wavelengths of light to be more abundant, and destructive interference causes other wavelengths to be less abundant. At different angles of view, the paths that rays of light travel within this multilayer reflector change, and these changes in path length cause a change in interference of the waves. This change in interference causes certain wavelengths of light to constructively interfere more when the angle of view is greater, and this leads to iridescence. In beetles, the multilayer reflectors usually contain chitin, a translucent polysaccharide similar in structure to cellulose, in at least one of the repeating layer, and the C. wallacei beetle shown above has air and chitin as its alternating layers.
What do we do?
We can measure colour at different angles, allowing us to measure iridescence. We record and analyse the colour of light being reflected off elytra by recording the wavelengths of the reflected light and their relative intensities. We do experiments with these elytra and then analyse any colour change. The spectrum of light here for example is of a (normal) green beetle elytron. |
How do we collect data?
We analyse colour and iridescence in beetle elytra using a spectrometer and a goniometer (Figure 4), and a specialist software called SpectraSuite. A spectrometer is a device that goes through every wavelength of light within a range and measures each wavelength's relative intensity, hereby producing a spectrum as shown above. The spectrometer we have can detect light with a wavelength of 350nm to 1000nm. A goniometer is a very accurate angle measuring device, and together with the spectrometer we can measure iridescence, as we can measure different colours at different angles. Using this set up, we are able to collect spectral data, and Figure 5 is an overlay of spectra of light reflected at different angles of incidence for a piece of elytron of the C. wallacei beetle:
We analyse colour and iridescence in beetle elytra using a spectrometer and a goniometer (Figure 4), and a specialist software called SpectraSuite. A spectrometer is a device that goes through every wavelength of light within a range and measures each wavelength's relative intensity, hereby producing a spectrum as shown above. The spectrometer we have can detect light with a wavelength of 350nm to 1000nm. A goniometer is a very accurate angle measuring device, and together with the spectrometer we can measure iridescence, as we can measure different colours at different angles. Using this set up, we are able to collect spectral data, and Figure 5 is an overlay of spectra of light reflected at different angles of incidence for a piece of elytron of the C. wallacei beetle:
In Figure 5, the wavelengths at which there are peaks in intensity are the most abundant colours of each spectrum. Although it is not very noticeable in this graph, the wavelengths of the peaks are decreasing as the angle of incidence is increasing, and this means that the main colour of light is changing as the angle of incidence changes. Thus, this elytron piece is iridescent.
What have we done and what are we doing?
One of the main research we conduct is for Extended Project Qualifications (EPQ), and several excellent papers have been produced in this manner. One of these EPQs, by Elsa Lawrence, investigated how physical changes in the environment affects the iridescence of a beetle. The physical changes she applied were short term heat treatment and sodium hydroxide (NaOH) treatment. In addition to this, we have taken a multitude of electron microscope images using the SEM of St Paul's School in London, and you can view some of these in the Images section of this website.
One of the recent experiments, led by Ilya Carey, investigated the permanent effects of heat treatment on the structure and colour of the C. wallacei elytra, for which there is some data you can view yourself. This investigation has concluded, and please feel free to have a look through the results.
What have we done and what are we doing?
One of the main research we conduct is for Extended Project Qualifications (EPQ), and several excellent papers have been produced in this manner. One of these EPQs, by Elsa Lawrence, investigated how physical changes in the environment affects the iridescence of a beetle. The physical changes she applied were short term heat treatment and sodium hydroxide (NaOH) treatment. In addition to this, we have taken a multitude of electron microscope images using the SEM of St Paul's School in London, and you can view some of these in the Images section of this website.
One of the recent experiments, led by Ilya Carey, investigated the permanent effects of heat treatment on the structure and colour of the C. wallacei elytra, for which there is some data you can view yourself. This investigation has concluded, and please feel free to have a look through the results.
Achievements:
1st of December 2016: 1st Structural Colour Symposium at Simon Langton Grammar School for Boys, where the Beetles Project was represented by Trishna Rai, Ifeoluwa Ifekoya, Niamh Alexander, Samy El Omda, Ilya Carey. Peter Vukusic and students from St Paul’s school were present.
10th March 2017: International Student Science Conference at St Paul’s School. The Beetles project was represented by Ilya Carey, and he won the award for Best Speaker at the event.
22nd March 2017: Freeze-fracturing of elytra with liquid nitrogen at the University of Kent with the help of Dr David Pickup and Dr Barbara Kirby, with Ilya Carey present.
April 2017: Scanning Electron Microscope (SEM) from St Paul's School used by Ilya Carey thanks to Dr James Perkins and under the supervision of Dr Kirby.
24th of May 2017: KM Charity make video of Beetles Project for the 2017 Bright Sparks Award, with Ilya Carey and Niamh Alexander.
29th of June 2017: Star Centre Symposium at Simon Langton Grammar School for Boys. The Beetles Project was represented by Ilya Carey.
7th of July 2017: KM Charity Bright Sparks Award at Discovery Park, Sandwich, where the project was one of the winners.
10th of July 2017: Ilya Carey’s Extended Project pertaining to the heat treatment of iridescent beetles submitted. The project was graded an A* (45/45).
16th of March 2018: International Student Science Conference at St Paul’s School. The Beetles project was represented by Andrew Nicoll and Ilya Carey.
18th of April 2018: Transmission Electron Microscope (TEM) used at the University of Kent, with the help of Dr Ian Brown. Aysha Wilson, Ilya Carey, and Andrew Nicoll were present.
2nd of July 2018: Andrew Nicoll’s Extended Project pertaining to the mathematical modelling of iridescent structures submitted.
1st of December 2016: 1st Structural Colour Symposium at Simon Langton Grammar School for Boys, where the Beetles Project was represented by Trishna Rai, Ifeoluwa Ifekoya, Niamh Alexander, Samy El Omda, Ilya Carey. Peter Vukusic and students from St Paul’s school were present.
10th March 2017: International Student Science Conference at St Paul’s School. The Beetles project was represented by Ilya Carey, and he won the award for Best Speaker at the event.
22nd March 2017: Freeze-fracturing of elytra with liquid nitrogen at the University of Kent with the help of Dr David Pickup and Dr Barbara Kirby, with Ilya Carey present.
April 2017: Scanning Electron Microscope (SEM) from St Paul's School used by Ilya Carey thanks to Dr James Perkins and under the supervision of Dr Kirby.
24th of May 2017: KM Charity make video of Beetles Project for the 2017 Bright Sparks Award, with Ilya Carey and Niamh Alexander.
29th of June 2017: Star Centre Symposium at Simon Langton Grammar School for Boys. The Beetles Project was represented by Ilya Carey.
7th of July 2017: KM Charity Bright Sparks Award at Discovery Park, Sandwich, where the project was one of the winners.
10th of July 2017: Ilya Carey’s Extended Project pertaining to the heat treatment of iridescent beetles submitted. The project was graded an A* (45/45).
16th of March 2018: International Student Science Conference at St Paul’s School. The Beetles project was represented by Andrew Nicoll and Ilya Carey.
18th of April 2018: Transmission Electron Microscope (TEM) used at the University of Kent, with the help of Dr Ian Brown. Aysha Wilson, Ilya Carey, and Andrew Nicoll were present.
2nd of July 2018: Andrew Nicoll’s Extended Project pertaining to the mathematical modelling of iridescent structures submitted.