Thursday, 18 July 2013

Large-flowered Evening Primrose (Oenothera glazioviana Micheli): UV-reflexion, simulated bee-colours and UV-induced fluorescence.

The genus Oenothera is mainly native in America. Several species have been brought to Europe as ornamental plants and some have escaped from there. Interestingly, there are stable hybrids in Europe that are not found in America. The species O. glazioviana is probably a hybrid that emerged in Europe. In contrast to most other Oenothera species O. glazioviana ( does not seem to be self-pollinating.
The species was determined with the following key:

Plants were collected in Bensheim, Germany July 2013  (growing in the garden of the author, as a weed).

The flowers show a very prominent UV-signature with a dark centre and dark veins while the outer parts of the petals show a strong UV reflexion. In the simulated bee-colours the petals appear bee-magenta (green plus UV) with a bee-red centre (only green reflexion), while the pollen is bee-yellow (reflecting green and blue but no UV). – Interestingly, the UV-signature becomes also visible to the human eye when the flowers are illuminated with a UV torch (see induces fluorescence image).

Visible light: Panasonic Lumix G1, broadband modified, EL-Nikkor 80 mm/f5.6 at f8.

Ultraviolet light: Panasonic Lumix G1, broadband-modified, EL-Nikkor 80 mm/f5.6 at f8. Baader U2" (Venus) filter, flash: “UV flash-it”. 

Monday, 8 July 2013

Butterfly: Marbled White (Melanargia galathea L.)

Marbled White (M. galathea) is a common butterfly species in central Europe found on meadows that are not farmed to intensively.
UV-photos of butterflies are challenging, since UV-captures normally require a tripod, manual focusing and exposure times that are too long for moving subjects. In this case I was out at sunset when this species was already sitting at the sleeping positions in the vegetation. Nevertheless, all attempts to capture an image with available light resulted in heavy motion-blur.

Photographed near Tauberbischofsheim, Germany  6 June 2013.

I have not captured or seen many UV images of butterflies, so far. 
In M. galathea the overall UV-reflexion of the wings is pretty weak and shows less contrast than in visible light. However, the blue dots are an exception in being very UV-bright, forming a strong contrast to the surrounding wing.

Images were taken with a broadband-modified Panasonic Lumix G1 and the EL-Nikkor 80mm/f5.6 at f5.6.

Visible light image with Baader UV/IR-blocking-filter, ISO 100

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

Since many butterfly species can see UV light it is not unlikely that there are more species with distinct UV pattern on their wings.