''Sternotomis callais'', the African longhorn beetle, is a species of
beetle
Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...
in the family
Cerambycidae
The longhorn beetles (Cerambycidae), also known as long-horned or longicorns (whose larvae are often referred to as roundheaded borers), are a large family of beetles, with over 35,000 species described.
Most species are characterized by anten ...
. It was described by
Léon Fairmaire
Léon Marc Herminie Fairmaire (29 June 1820 – 1 April 1906) was a French entomologist.
As a specialist in Coleoptera, he assembled an immense collection comparable with that of Pierre François Marie Auguste Dejean (1780–1845). This is in the ...
in 1891. It is known from
Cameroon
Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the R ...
, the
Republic of the Congo
The Republic of the Congo, also known as Congo-Brazzaville, the Congo Republic or simply the Congo (the last ambiguously also referring to the neighbouring Democratic Republic of the Congo), is a country located on the western coast of Central ...
, the
Democratic Republic of the Congo
The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...
,
Equatorial Guinea
Equatorial Guinea, officially the Republic of Equatorial Guinea, is a country on the west coast of Central Africa. It has an area of . Formerly the colony of Spanish Guinea, its post-independence name refers to its location both near the Equ ...
, and
Angola
Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...
. It feeds on ''
Coffea liberica var. dewevrei''.
Brilliant green coloration
The scales on the African longhorn beetle exhibit a brilliant green color due to a
photonic crystal
A photonic crystal is an optical nanostructure in which the refractive index changes periodically. This affects the propagation of light in the same way that the structure of Crystal structure, natural crystals gives rise to X-ray crystallograp ...
-like periodic cuticle network, and the three-dimensional network of the cuticle was found to be modelled appropriately by the I-WP photonic crystal.
Although described mathematically in 1970, this is the first time this kind of photonic crystal structure has been observed in nature.
The I-WP-type minimal surface was mathematically found by Schoen in 1970, was named "I-graph-Wrapped Package graph surface" because it reminded Schoen of the arrangement of string on a simply wrapped package.
The wavelength range of the green color corresponds to the frequency of the photonic band gap.
References
Sternotomini
Beetles described in 1891
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