Many of the visitors to the Manchester Museum’s Entomology store are researchers, studying various aspects of insect diversity, taxonomy and even physical properties of their colour. A group of researchers from the New Castle University (UK) is interested in what could be a real colour of butterflies and moths seen as if through the eyes of their predators, birds in particular. Here is a brief report provided by Matthew Wheelwright (Fig. 1), a postgraduate student who is involved in this research project:
Fig. 1. Matthew Wheelwright, a postgraduate student from the New Castle University (on the left) and Phillip Rispin, a curatorial assistant from the Manchester Museum (on the right), are sorting out lepidopteran specimens for scanning.
Colour is vitally important for many aspects of insect lives. It can help them to control their body temperature, or allow them to be recognised by members of their own species. The right body/wing colour can allow insects to blend into their environment in order to hide from predators. Another way in which colour can be used to escape predation is through giving a clear message to their potential predators that they are toxic, not edible or unpleasant tasting and should therefore be avoided. Such insects are usually brightly coloured, with a mixture of yellow/orange and black stripes and spots on their wings. This phenomenon is known as warning coloration (=aposematism). Some other species which occur in the same areas can also benefit from these warning signals by evolving to look like these not edible species; this phenomenon is known as mimicry.
Fig. 2. Butterflies and moths from the collection of the Manchester Museum sorted out for scanning by means of a hyperspectral camera.
The purpose of our study is two-fold. Firstly we want to find out what makes a good pattern of warning coloration and secondly to discover how closely a mimic must resemble a model having warning coloration (=aposematic model) in order to deceive predators into thinking that they are the same species. In order to do this, we need to know how these patterns look to predators (many of which have different visual systems to humans). We therefore take pictures of specimens from various collections from across the globe, including the entomology collection at the Manchester Museum (Fig. 2), using a hyperspectral camera (Fig. 3). This camera allows us to look at the exact colour spectrum of the specimens, including the amount of Ultraviolet (UV) reflected by them. The latter aspect is very important, as many predators, such as birds, can see in UV.
Fig. 3 A hyperspectral camera at work, scanning the Black Witch Moth (Ascalapha odorata) from the collection of the Manchester Museum.
We then used models of predator visual systems to quantitatively compare the colour and pattern of aposematic species to non-aposematic species and the patterns of mimics and models to predict how the predators could perceive them and therefore react to them. In other words, we try to see butterflies and moths through the eyes of insect predators and hope to find out whether insects that look aposematic to us (or their mimics) are seen in the same way by their predators.
Two images of the Orange Sulphur (Colias eurytheme) given below (Fig. 4) show how the butterfly appears to humans (on the left) and to a bird (on the right). Orange Sulphur looks iridescent under the UV, and the false colour image on the left contains the purple representing where the UV is the brightest and seen to birds. The image was kindly created for us by Olivier Penacchio of the University of St. Andrews.
Fig. 4. Two views of Orange Sulphur (Colias eurytheme): left – as seen by a human; right – as could be seen by a bird (contains the purple representing where the UV is the brightest). © Olivier Penacchio
Such research project would be impossible without access to museum specimens from large entomological collections such as that of the Manchester Museum. So we would like to take this opportunity to thank Dr Dmitri Logunov and Phil Rispin for their assistance and generosity with the loan of some specimens.
Entomology Manchester 