Scale (butterfly)

from Wikipedia, the free encyclopedia
Edge of a moth's wing with lamellar scales,
section approx. 600 µm × 600 µm in approx. 200-fold magnification under a polarizing filter

The scales of the butterflies can be found on the top of their wings and are also called "butterfly dust". They are characteristic of the order of the butterflies and gave their name to their scientific name as "Lepidoptera" (from ancient Greek λεπίδος lepidos , German 'scales' and πτερόν pteros , German 'wing' ). Dandruff can also be found on the head (caput), chest ( thorax ) and abdomen ( abdomen ) and genitals. The scale is the smallest mosaic-shaped part of the coloring of the butterfly wing. The scaling of the butterflies always only refers to their adult forms , the fully developed adults .

Apart from butterflies, only a few caddis flies have similar scales on their wings, e.g. B. the African species Pseudoleptocerus chirindensis .

shape

The scales are mostly hollow structures, only a few primitive moths (ancient moths , Micropterigidae) form compact scales. Based on their external shape, they can be divided into three classes:

construction

Below the upper edge of their underside, the scales have a pin-shaped design , similar to roof tiles . This is hooked into a cylindrical shape on the upper side of the wing of the butterfly. The hooking can be released mechanically, with which the scale is irreversibly detached from the wing without causing further injuries.

The outer surface of the scales is finely structured (often parallel groove-shaped), while the side lying on top is smooth.

The main material of the scales, like that of the cuticle, consists of chitin . It has a refractive index of 1.58 against air .

  • Scanning electron microscope (SEM) image of a scaled wing of Inachis io (× 50)

  • SEM image of a lamellar scaly wing (× 200)

  • SEM image of lamellar wing scales (× 1000)

  • SEM image of the fine structure of a scale (× 5000)

Coloring and reflection

The color and reflection pattern of the butterfly wing results from the mosaic-shaped interaction of many thousands of individual scales as well as the physical interaction of absorption and reflection of the incident light on the wing.

Dyes

The dark coloring of the wings is mainly achieved by pigmenting the scales with melanin , which absorbs light . Each scale is essentially one color, there are color gradients.

UV pattern

Some knight butterflies produce UV wing patterns either through UV absorption or UV reflection in order to be able to exchange species-specific signals (e.g. for territorial delimitation or search for partners), which are hardly recognized by their predators .

Polarization pattern

Some strikingly colorful butterfly wings produce polarization patterns , which are usually not created by the scales, but rather by the microstructures of the underlying cuticle. The transparent scales (glass scales) of the knight butterfly (like Graphium sarpedon ) can generate polarization patterns.

Microstructures on the scales of the Papilio palinurus create a bright green, consisting of reflections of blue and yellow light.
Papilio palinurus : bright green from double reflection of blue and yellow

Reflection effects

Striking reflection patterns (metallic sheen, iridescence, shimmering, iridescence) are often only produced by one of the sexes . Strong light reflections enable intraspecific signals over greater visual distances.

Special reflective properties are created by the interference of light on fine surface structures ( called structure color). The microstructures are mainly made up of chitin. Reflection patterns can reflect light that is visible to humans, such as UV light as an irradiation source, and emit visible light or UV light, sometimes as a polarization pattern. The reflection patterns can depend on a large number of properties of the light source such as the surface structures. It is true that the microstructures on which the reflection is based must have the same order of magnitude as the wavelength of light. The basic element is called a photonic crystal . These structures have to repeat themselves periodically more often in order to z. B. Bragg reflections , such as. B. in the often occurring fine corrugation (which can be seen well in the SEM images above).

Bragg reflection ,
left additive interference , right subtractive

Examples

  • Many blues create a color shimmer to a different colored base color. In order to analyze the underlying microstructures, the structure grids were examined. Albulina metallica creates strong yellow-green reflection patterns through relatively evenly arranged layered microstructures. Cyanophrys remus generates reflection patterns through long dorsally and short microstructures ventrally.
Male Greater Schiller Butterfly : brown due to pigmentation, purple due to reflection at 380 nm ± 50 nm
  • The typical iridescence of the common Schiller butterflies (both for Apatura ilia and Apatura iris ) is caused by special cavities in the scales of the male animals, while the scales in both sexes are pigmented brown. The reflection in the purple range is at a wavelength of 380 nm ± 50 nm and only emerges at an angle of 18 °. The reflections are created by the interaction of two types of scales. Type I is on top, Type II below. Type I produces the shimmering reflection effect due to its nanostructures, similar to that of morpho butterflies .
  • Some morpho species produce shimmering reflections through the microstructures of their scales. In the blue laser it could be determined experimentally in two ways that up to 75% of the blue light is reflected at different angles of incidence. Interferences between two layers of scales play a role, the upper layer being largely transparent (without pigmentation), while the lower layer has more complex fine structures on its surface.

  • Blue morpho butterfly : Radiant blue due to double reflection on transparent and pigmented scales

  • Morpho cypris : brilliant blue through reflection

  • Morpho cypris : largely brown pigmentation with flat lighting

Papilio ulysses : Radiant light blue through UV double reflection
  • Some male Papilio species show a very effective reflection behavior , for example Papilio ulysses and Papilio blumei . They are easily distinguishable in visible light. P. ulysses shows two reflection maxima under UV light . One comes from a micro-depression, the other from a micro-elevation on its scales. The reflection maxima change at different angles of UV incidence. The bright light blue color of P. ulysses is made up of two different spectral colors , which alternate depending on the incidence of UV light. P. blumei has similar fine structures, but changes in the angle of incidence have no effect; it has only one reflection maximum in the green area, which is however clearly pronounced. Here the blue reflection is due to the strong polarization effects of its scale microstructures.

  • Papilio blumei : green due to pigmentation

  • Papilio blumei : blue due to polarized reflection and green pigmentation

Functions

Wing pattern

The wing pattern plays a variety of roles in camouflage , possible mimesis , warning coloring , mimicry , choice of partner and intra-species communication.

The purposes of camouflage and mimesis (phytomimesis) are evident in many inconspicuous or form-dissolving wing patterns.

Illustration by Henry Walter Bates (1862). The upper and third rows show Dismorphia species ( mimicry ), the second and the last row show Ithomiini species ( Aposematism ).

Warning coloring

Some clearly high-contrast patterns, especially with large structured yellow and red components, are interpreted as warning color ( aposematism ), especially when their carriers carry toxins for their possible predators (e.g. Ithomiini species, Altinote dicaeus callianira ).

mimicry

Mimicry (or Bates' mimicry ) is e.g. B. attributed to the large spots of the peacock eye as pseudo eyes , which imitate a vertebrate eye when it flies up . Mimicry also includes the imitation of aposematistically colored animals of another species, but without toxins.

Internal communication

Gender- specific patterns are of particular importance when looking for a partner, choosing a partner and marking the area . Particularly conspicuous phenomena of the wing pattern enable signals to be passed on over greater visual distances and often play a role in intra-species communication, but the sudden display when opening the wings can also have a strong signal effect and trigger a panic-like flight reflex of other individuals.

Since UV and polarization patterns are hardly recognizable for vertebrate eyes, these special pattern shapes offer a good opportunity for intra-species signal transmission without attracting the attention of predators.

Buoyancy aid

As a hollow body, the scales contribute to the ability to fly and give stability to the flapping of the wings. When the wings move upwards, they are pressed onto the ground and behave aerodynamically, but since they are loosely moveable, they exert additional air resistance when moving downwards, which means less muscle work is required and a braking effect is achieved when lowering for landing maneuvers.

The loss of large parts of the scaling can therefore impair flight behavior and the ability to fly.

Camouflage the clutch

Various female butterflies camouflage their clutches with some wing scales ( called anus wool ) when they lay eggs . B. owl moth , spring cross-wing , southern peacock butterfly .

Heat storage

Melanin in the dandruff can serve as a heat absorber and store and the stored solar heat can be released into the body. Dark wing patterns in Weißlingen ( Pieris ) could be related to differential body heat distribution.

Wax flakes

Myrmecophilic butterflies that have recently hatched in an ant's nest, such as blue ants, can escape because they have guarded scales, which irritate the chase ants and prevent them from overwhelming the young butterfly for a while.

Tufts of scales to control

Pigeon tails use special elongated scales, which look like tufts of hair and which contributed to the naming of the animals, to control their hummingbird-like hovering behavior .

Scented scales

Many male colia species and monarch butterflies have scented scales that resemble other "normal" scales, but help disperse pheromones to attract females. So that the pheromones are not blown away by wing flaps and wasted, the scent scales sit on the upper sides of the hind wings at a point where the front and rear wings overlap.

Evolutionary development

The phylogenetic development of the butterfly scales was a crucial property that distinguishes butterflies from other insects. The scales developed from the sensory bristles of common insect ancestors. The scales are z. B. homologous to the sensory bristles of Drosophila , corresponding genes have been characterized as homologous. Since few caddis flies have similarly scaled wings, the two orders Lepidoptera and Trichoptera are traced back to a common ancestor Amphiesmenoptera .

Individual evidence

  1. ↑ a b c d e What is butterfly dust? . Planet knowledge. Retrieved March 7, 2013.
  2. ↑ a b c d e Ron Galant, et al. : Expression pattern of a butterfly achaete-scute homolog reveals the homology of butterfly wing scales and insect sensory bristles . (PDF) In: Current biology . 8, No. 14, July 2, 1998, pp. 807-813. doi : 10.1016 / S0960-9822 (98) 70322-7 .
  3. ↑ a b c d e f g MJ Scoble: The Lepidoptera: Form, Function, and Diversity . 2005, page 63 ( limited preview in Google Book Search, accessed August 21, 2009).
  4. ↑ John Huxley, Peter C. Barnard: Wing ‐ scales of Pseudoleptocerus chirindensis Kimmins (Trichoptera: Leptoceridae) . In: Zoological journal of the Linnean Society . 92, No. 3, March 15, 1988, pp. 285-312. doi : 10.1111 / j.1096-3642.1988.tb01514.x .
  5. ↑ Heinz Schumacher, deputy chairman of the Working Group of Rhenish-Westphalian Lepidopterists, quoted by
    What is butterfly dust? . Planet knowledge. Retrieved March 7, 2013.
  6. ↑ a b c d e f L. P. Biró, et al. : Living photonic crystals: butterfly scales — nanostructure and optical properties . In: Materials Science and Engineering . C 27, No. 5-8, 2007, pp. 941-946. doi : 10.1016 / j.msec.2006.09.043 .
  7. ↑ a b P. Vukusic, JR Sambles and CR Lawrence: Structural color: Color mixing in wing scales of a butterfly . In: Nature . 404, No. 6777, March 30, 2000, pp. 457-457. doi : 10.1038 / 35006561 .
  8. ^ A b Mason CW: Structural colors in insects. II . In: The Journal of Physical Chemistry . 31, No. 3, January 1926, p. 321. doi : 10.1021 / j150273a001 .
  9. ^ Robert E. Silberglied, OR Taylor: Ultraviolet differences between sulfur butterflies, Colias eurytheme and Colias philodice , and a possible isolating mechanism . In: Nature . 241, 1973, pp. 406-408.
  10. ^ Robert E. Silberlied: Communication in the ultraviolet . In: Annual Review of Ecology and Systematics . 10, 1979, pp. 373-398.
  11. ↑ Jonathan M. Douglas, et al. : Light habitats and the role of polarized iridescence in the sensory ecology of neotropical nymphalid butterflies (Lepidoptera: Nymphalidae) . In: The Journal of Experimental Biology . 210, May 1, 2007, pp. 788-799. doi : 10.1242 / jeb.02713 .
  12. ↑ Doekele G. Stavenga, et al. : Glass scales on the wing of the swordtail butterfly Graphium sarpedon act as thin film polarizing reflectors . In: The Journal of Experimental Biology . 215, No. 4, February 15, 2012, pp. 657-662. doi : 10.1242 / jeb.066902 .
  13. ↑ Doekele G. Stavenga, Marco A. Giraldo, Hein L. Leertouwer: Butterfly wing colors: glass scales of Graphium sarpedon cause polarized iridescence and enhance blue / green pigment coloration of the wing membrane . In: Journal of Experimental Biology . 213, No. Pt 10, 2010, pp. 1731-1739. PMID 20435824 .
  14. ↑ a b c d Vukusic P., et al. : Quantified interference and diffraction in single Morpho butterfly scales . In: Proceedings of the Royal Society of London Series B: Biological Sciences . 266, No. 1427, 1999, pp. 1403-1411. Retrieved March 11, 2013.
  15. ↑ P. Vukusic, JR Sambles and H. Ghiradella: Optical classification of microstructure in butterfly wing-scales Archived from the original on November 8, 2006. In: Photonics Science News . 6, 2000, pp. 61-66.
  16. ^ Ro Prum, T. Quinn, Rh. Torres: Anatomically diverse butterfly scales all produce structural colors by coherent scattering . (Free full text) In: The Journal of experimental biology . 209, No. Pt 4, February 2006, ISSN  0022-0949 , pp. 748-765. doi : 10.1242 / jeb.02051 . PMID 16449568 .
  17. ↑ GI Márk, Z. Vértesy, K. Kertész, Z. Bálint, LP Biró: Order-disorder effects in structure and color relation of photonic-crystal-type nanostructures in butterfly wing scales . In: Phys Rev E Stat Nonlin Soft Matter Phys . 80, No. 5 Part 1, November 9, 2009. PMID 20365002 .
  18. ↑ a b Dejan Pantelić, et al. : High angular and spectral selectivity of purple emperor (Lepidoptera: Apatura iris and A. ilia) butterfly wings . In: Optics Express . 19, No. 7, 2011, pp. 5817-5826. doi : 10.1364 / OE.19.005817 .
  19. ^ J. Heath, Emmet A. Maitland: The moths and butterflies of Great Britain and Ireland . tape 7 , no. 1 . Harley Books Ltd., Colchester 1989, ISBN 0-946589-25-9 .
  20. ↑ Srećko B. Ćurčić, et al. : Micro ‐ and nanostructures of iridescent wing scales in purple emperor butterflies (Lepidoptera: Apatura ilia and A. iris) . In: Microscopy Research and Technique . 2012. doi : 10.1002 / jemt.22021 .
  21. ^ Ying-Ying Diao, Xiang-Yang Liu: Mysterious coloring: structural origin of color mixing for two breeds of Papilio butterflies . In: Opt Express . 19, No. 10, May 9, 2011, pp. 9232-9241. doi : 10.1364 / OE.19.009232 . PMID 21643177 .
  22. ↑ Aposematic colors ( en ) Retrieved March 9, 2013.
  23. ↑ Diematic patterns ( en ) Retrieved March 9, 2013.
  24. ^ Saturniidae of Europe. AR Pittaway, accessed March 22, 2011 .
  25. ^ Differences between Saturnia pavonia and Saturnia pavoniella in Central and Southern Europe. (PDF; 609 kB) Wolfgang A. Nässig, accessed on March 22, 2011 .
  26. ^ Joel G. Kingsolver: Thermoregulatory significance of wing melanization in Pieris butterflies (Lepidoptera: Pieridae): physics, posture, and pattern . In: Oecologia . 66, No. 4, 1985, pp. 546-553.
  27. ↑ Heiko Bellmann : The new Kosmos butterfly guide, butterflies, caterpillars and forage plants . Franckh-Kosmos, Stuttgart 2003, ISBN 3-440-09330-1 , p.  150 .
  28. ↑ Lennart Lundgren, Gunnar Bergström: Wing scents and scent-released phases in the courtship behavior of Lycaeides argyrognomon (Lepidoptera: Lycaenidae) . In: Journal of Chemical Ecology . 1, No. 4, 1975, pp. 399-412.
  29. ^ Paul Whalley: A review of the current fossil evidence of Lepidoptera in the Mesozoic . In: Biological Journal of the Linnean Society . 28, No. 3, June 28, 2008, pp. 253-271. doi : 10.1111 / j.1095-8312.1986.tb01756.x .