This stunning little butterfly gets its name from the metallic blue-green ‘studs’ found on the underside of the hindwings, just beyond the orange spots. Apart from these studs, males are best identified by the thick black borders on their blue upperwings. Females are more challenging and can resemble a faded brown argus.
A guide to the blue butterflies
Butterfly expert Alan Sumnall offers a thorough guide to one of our most enchanting groups of butterflies – the blues.
The blue butterflies are some of the most stunning insects to be found in the UK. To many, they are the optimal sight on a hot summer’s day spent on a species-rich grassland.
Not all are constrained to grasslands though, and they make use of a wide variety of habitats. They belong to a subfamily called the Polyommatinae, with nine resident species in the UK.
The name ‘blue’ can be confusing, as some species show strong sexual dimorphism (where males and females look very different), with females being predominantly brown. In some species, neither sex is blue at all.
Blue butterflies and ants
Most blue butterflies have a close relationship with ants, a phenomenon called myrmecophily. In this subfamily, the larvae produce a sweet secretion from a ‘honey’ gland, which is a food source to ants. The ants are attracted to this and tend to the larvae, who in return are offered a level of protection from potential predators and parasites.
As we will discover, this relationship is not essential for all blue butterflies, whereas others are dependent on ants to complete their life cycle – sometimes to the detriment of the ants.
Identifying blue butterflies
Some species are easy to identify, but others can be difficult to distinguish and rely on closer inspection, particularly of the markings on the undersides. It can help to know which larval hostplants are used for egg-laying, and therefore each species’ preferred habitat, as well as the months in which they’re flying.
Some species are single brooded (only one generation each year), while others can have second and even third broods.
We will have a look at each species, with tips on where and when to look for them, and key features to confirm identification. If you want to jump ahead to a specific butterfly, click on the name below:
Mission Blue Translocation Project Pilots New Release Approach
May 2019 – A shared commitment to the recovery of endangered Mission blue butterfly populations often brings land managers together from across the Bay Area to coordinate and exchange ideas. At one such meeting, Golden Gate National Parks Conservancy staff were presenting their work on the Mission Blue Butterfly Translocation project at Milagra Ridge when another biologist, Jessica Appel, shared an observation. She recalled that during her PhD research on Acmon blue butterflies, the females laid more eggs after being fed sugar water in a lab setting.
Christina Crooker, a coordinator of the translocation project, took note. It was unusual for translocated Mission blues to lay eggs upon their release. Yet project data showed that it was possible. Some had laid eggs while they were released under netting during the first year of translocations. Could feeding the butterflies help support that behavior?
A challenge with feeding butterflies sugar water outside of a lab is that if the water gets on the butterfly, it could attract ants. So Christina reached out to Jessica to brainstorm safe ways of feeding butterflies in the field. Ideas in hand, they followed up with the US Fish and Wildlife Service to review options. This month, the agency approved a pilot effort to test feeding half of translocated females.
In their first pilot experiment of this approach, staff released three female butterflies fed sugar water, and three not fed sugar water, with promising results. The sugar water-fed butterflies laid a total of 14 eggs, while the butterflies not fed sugar water laid a total of one egg. Staff even recorded one sugar water-fed female in what may be the first-ever video of a Mission blue butterfly laying an egg!
Embed
Embed Video
Close Copy
Visit our keyboard shortcuts docs for details Duration: 26 seconds
Under mesh netting, a Mission blue butterfly walks around on vegetation, and lays an egg on a lupine leaf. Other tiny white eggs are visible on other leaves of the same plant. This may be the first video ever to capture a Mission blue butterfly laying an egg!
Translocations are now done for this season, but more are planned for next year. Given the preliminary success of this pre-release feeding, further trials are likely to continue next year as well. Repeating the trials several times will help ensure that this approach is as reliable, safe, and effective as possible. If all goes well, butterfly conservationists may have a powerful new tool in their toolkits!
Contact Christina Crooker to learn more.
Something blue – butterfly wings
There are plenty of blue organisms in the world, but blue is nevertheless the rarest pigment found in nature. Most blue colours are produced by physical effects and are called structural colours. There are no true blue pigment in plants and thus no true blue flowers! There are blue flowers of course, but they produce this colour using modified red (anthocyanin) pigments.
Many blue colours in nature – from blue eyes to the blue sky – are caused by Tyndall scattering. Blue occurs because of the presence of tiny particles (or voids) about the same size as the wavelength of blue light (c. 500 nm). The smaller wavelengths (blue and violet colors) of the incident white light are scattered, and the longer wavelengths (red and yellow) pass undisturbed through the medium.
In butterflies like the beautiful blue Morpho (below), structural blue colours are produced by interactions between incident light and reflections caused by surface structures on the wing scales. All structural colours produced by butterfly scales are as a result of what is termed coherent scattering (Prum et al., 2006). That is to say, ‘constructive interference’ between light waves scattered coherently by the nano-structures on the surfaces of the scales. Thin-film interference effects from the wing scales enhance the blue color and produces extra reflection peaks in the infrared and ultraviolet regions.
The scales on the wings are blue Morphos – and many other shiny blue butterflies – are covered with microscopic ridges running longitudinally down the scale (about 1,300 thin, parallel ridges per mm). This patterning creates a periodic or repeating structure – called a diffraction grating – in the horizontal scale plane. The ridges are constructed of a series of overlapping lamellae – called a multilayer system – each about 90-100 nm thick (depending on species), which in cross-section, appear as Christmas (or pine) tree-like geometric shapes running perpendicular to the longitudinal plane of the scale (see below).
These tiny stacked layers (e.g. 10-12 multi-layers) of cuticle stick out on either side of the thousands of ridges running the length of the scales, and produce interference effects in the blue part of the visible spectra. It is the interference in light between these layers of air and cuticle (with their different refractive indices) which produces the iridescent colours of the blue butterflies.
It is thought that these nano-structures are physiologically costly for an organism to produce, and as such they are good, honest indications of the quality of a butterfly. Not surprising therefore, some male butterflies display highly reflective blue UV patches to females, during courtship dances, and to other males, in territorial disputes. The brightness of these iridescent UV patches in the common eggfly, Hypolimnas bolina (below) appears to be a crucial factor in attracting females and achieving successful mating (Kemp, 2007). Males of this species have oval-shaped areas of bright blue/UV iridescence on the dorsal (upper) sides of both fore- and hind-wings.
The female Hypolimnas bolina butterflies lack these bright blue patches (below) but they do have some blue wing scales arranged in tiny blue spots.
Some butterflies do produce bluish colours – not true blue – using pigments. For example, the Common bluebottle, Graphium sarpedon (below) has wings in which the central bands have high concentrations of a bile pigment, called sarpedobilin. This molecule is combined with a strongly blue-absorbing carotenoid, lutein, resulting in blue-green or green coloured wing patches (Stavenga, 2010). These colored patches lack the usual wing scales found on the rest of the wing.
The pigment pterobilin also provides green for patches on the wings of the Tailed jay, Graphium agamemnon (below). Another butterfly which manages to get a blue colour from the same pigment, pterobilin, is the obrina olivewing, Nessaea obrinus.
So, whether it is by physics or chemistry, butterflies have evolved many ways of producing blues and greens, but true blue is – I think – always produced via the wonders of nanoarchitechtrure, microscopic patterns on the surfaces of the wing scales which do magic with the light simply by using the different light refracting properties of chitin and air.
References
Kemp, D.J. (2007a) Female butterflies prefer males bearing bright iridescent ornamentation. Proceedings of the Royal Society of London B: Biological Sciences, 274(1613), 1043-1047.
Prum, R. O., Quinn, T., & Torres, R. H. (2006). Anatomically diverse butterfly scales all produce structural colours by coherent scattering. Journal of Experimental Biology, 209(4), 748-765.
Stavenga, D. G., Giraldo, M. A., & Leertouwer, H. L. (2010). Butterfly wing colors: glass scales of Graphium sarpedon cause polarized iridescence and enhance blue/green pigment coloration of the wing membrane. Journal of Experimental Biology, 213(10), 1731-1739.
