Common Blue, Polyommatus icarus, Rottemburg, 1775 (Lepidoptera, Lycanidae). Butterfly photographed in visible and ultraviolet light.

Photographed near Burgarach, Southern France 29 July to 8 August 2013.

Polyommatus icarus is one of the most common species of the family Lycanidae. This species has a Palaearctic distribution. The caterpillars feed on the various species of Fabacea (e.g. Lotus spp., Lathyrus spp., Trifolium spp., Astragalus spp.).

Similar to the species Polyommatus coridon that was published here before (http://bee-colours.blogspot.de/2013/09/chalkhill-blue-polyommatus-coridon-poda.html) the outside or

“downside” of the wings has a UV-reflection that doesn’t make the animal stand out from the

background. However, in P. icarus the visibly black and red marks on the wings show a stronger contrast compared to the rest of the wing because they are entirely UV-black.

The insides, or upper sides, of the wings that are only visible in active animals and appear to humans in bright blue have a very strong UV-reflexion. This makes the blue (inner) sides of the wings appear much brighter than the background in the UV-capture.

UV images were taken with a broadband-modified Panasonic Lumix G1 and the EL-Nikkor

80mm/f5.6 at f8.

Visible light image: Panasonic Lumix GH2 (unmodified) with Tokina AT-X 90 mm Macro.

image reference: CHA_P1200160_130731

Visible light image: Panasonic Lumix G1 with EL-Nikkor 80/f5.6, Baader UV/IR-cut-filter:

 image reference: CHA_P1100266_130729

UV-image, Baader U-filter 2”, ISO 400, UV-flash MR21N:

image reference: CHA_P1100271_130729

crop from the image above:

UV-image, Baader U-filter 2”, ISO 400, UV-flash MR21N:

image reference: CHA_P1100629_130808

 

Chalkhill Blue (Polyommatus coridon, Poda, 1761): Male butterfly photographed in visible and ultraviolet light.

Polyommatus coridon is a butterfly of the family Lycanidae. This species has a Palaearctic distribution. It requires habitats with calcareous soil where the plant Hippocrepis comosa (Fabaceae) can grow, since the caterpillars feed on the latter.
Many butterfly eyes, like in other insect groups are sensitive to UV-light. Therefore, the UV-reflection of their wings might play a role in their intra-species signalling. There is also literature evidence for that hypothesis, e.g. Knüttel and Fiedler (2000).
In this P. coridon the UV pattern on the outside of the wings is dominated by a pretty low reflection. The legs and hairs of the head and body are significantly more reflective. On the other hand, the inner sides of the wings which appear blue in human vision, and are only visible when the animal is active, are much more UV-reflective. The same is true for the outside part of the first wing that is hidden, when the wings are folded and the animal is resting.
So a working hypothesis could be that the outside has sort of an UV-camouflage, while the blue colour of the wing that is only found in males has a signalling function reaching into the UV-spectrum.

Photographed near Burgarach, Southern France 1 & 8 August 2013.
 
All UV-images were taken with a broadband-modified Panasonic Lumix G1 and the EL-Nikkor 80mm/f5.6 at f8.



Visible light image: Panasonic Lumix GH2 (unmodified) with Tokina AT-X 90 mm Macro. (resting animal, outside of the wings):

image reference: CHA_P1200183_130801


Visible light image: Panasonic Lumix GH2 (unmodified) with Tokina AT-X 90 mm Macro. (active animal, inner side of the wings):

image reference: CHA_P1200639_130808

UV-image, Baader U-filter 2”, ISO 400, UV-flash MR21N, (resting animal, outside of the wings):

image reference: CHA_P1100363_130801

UV-image, Baader U-filter 2”, ISO 400, UV-flash MR21N, (active animal)

image reference: CHA_P1100686_130808

UV-image, Baader U-filter 2”, ISO 400, UV-flash MR21N, (active animal)

image reference: CHA_P1100689_130808

Literature:
Helge Knüttel and Konrad Fiedler: On the use of ultraviolet photography and ultraviolet wing patterns in butterfly morphology and toaxonomy: Journal of the Lepidopterists' Society 54(4), 2000, 137-144.