Butterfly Wing Scale Digital Image Gallery
Western Blue Butterfly
Appearing as if they were gliding sapphires, western blue butterflies grace the tropical rainforests of Cameroon, Uganda, and Sierra Leone. Brilliant blue iridescent upper wing surfaces are contrasted against navy blue backgrounds of the aptly named species. The swift African insects feature very large bodies and wings, which are remarkably thick and durable and enable some to reach speeds of 40 miles per hour in flight.
Scientifically known as Charaxes smaragdalis, the western blue butterfly species is highly variable and is represented by eleven recognized subspecies. As members of the brush-footed butterfly family, western blues possess a highly modified first pair of legs. The lower surfaces of their sizeable forewings and hind wings are shades of brown and tan and are covered in markings that help the butterflies blend into tree trunks, branches, and twigs. The species displays a moderate amount of sexual dimorphism and males are brighter and somewhat smaller in size than females. Also, in some subspecies, females display a broad median white band on their forewings, while others exhibit a blue band.
Specialization by the western blue butterfly and its congeners for host and food plants helps divide limited plant resources into narrow niches, thereby reducing competition, preventing hybridization, and increasing total butterfly numbers in the African rainforests. Female western blue butterflies lay their eggs on tropical plants including acacias, aspen trees, mahogany beans, and craib trees, and newborn caterpillars forage for leaves on the plants on which they were born. Although acacias are famous for their co-evolved communities of guardian ants, which prevent most kinds of herbivory, the adaptation appears to have little impact on the hardy western blue caterpillars.
Due to their incredible speed, western blue butterflies are nearly impossible to catch in flight and, historically, butterfly hunters had to patiently wait for individuals to rest or sun themselves, which made the elusive flying jewels highly valuable as specimens. However, when it was discovered that baits of dung and fermenting fruits lured adults to screen traps, western blues became much more common in butterfly collections. Still relatively valuable, in the underdeveloped nations of Africa money earned from butterfly collecting can help support economically struggling families and villages.
Cynthia D. Kelly, Shannon H. Neaves, Laurence D. Zuckerman, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
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