Urine can be "seen" in the UV helping birds of prey find rodents. Berries differ in their UV reflectance. Some example images of flowers and berries are available at http://www.uv4plants.org/gallery/plants-and-flowers-in-vis-and-uv-images/ as pairs of visible and UV images. Images are from Lasse Ylianttila.

Below are links to some publications I am aware of, but my expertise is more on plants than on animal vision.

http://www.nature.com/nature/journal/v373/n6513/abs/373425a0.html

http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0706.2002.980315.x/abstract

http://rspb.royalsocietypublishing.org/content/royprsb/266/1433/2125.full.pdf

http://onlinelibrary.wiley.com/doi/10.1034/j.1600-048X.2002.330212.x/abstract

http://www.uv4plants.org/gallery/plants-and-flowers-in-vis-and-uv-images/

as far as I know scorpions do, but it might be interesting for you to check on other Arachnids and e.g.  the webbings of Argiope (especially the stabilementum).

I recommend yellow bee-pollinated flowers as UV-reflectant; some Oenothera species reflect UV-light very strong.

With respect to scoprions: These animals show fluorescence under UV-light and glow blue.

Urine can be "seen" in the UV helping birds of prey find rodents. Berries differ in their UV reflectance. Some example images of flowers and berries are available at http://www.uv4plants.org/gallery/plants-and-flowers-in-vis-and-uv-images/ as pairs of visible and UV images. Images are from Lasse Ylianttila.

Below are links to some publications I am aware of, but my expertise is more on plants than on animal vision.

http://www.nature.com/nature/journal/v373/n6513/abs/373425a0.html

http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0706.2002.980315.x/abstract

http://rspb.royalsocietypublishing.org/content/royprsb/266/1433/2125.full.pdf

http://onlinelibrary.wiley.com/doi/10.1034/j.1600-048X.2002.330212.x/abstract

http://www.uv4plants.org/gallery/plants-and-flowers-in-vis-and-uv-images/

Many coral reef organisms reflect UV radiation 

If you are looking for some information on the UV structural colour in birds maybe the most interesting compilation is:

Prum. 2006. Anatomy, physics, and evolution of structural colors. In Hill, G. E., & McGraw, K. J.(Eds) (2006). Vol. 1: Mechanisms and measurements. Cambridge, MA [etc.]: Harvard University Press.

I'ts a bit old but may be a good start.

For iridiscent plumage look for the Osorio's work. 

people have impression that natural things reflect UV  mostly in nature UV is avoided cause it has degradation ability for DNA this is a mutagen also but some of the animals have developed skills to see UV light or emit them for reproduction purposes 

I my view those ecosystems mostly desert fauna/flora  has maximum capacity to tolerate or reflect UV mostly insects chitin have this ability  

In order to complete our list of UV-reflecting natural onjects I would suggest gloss from water and green leaf and other smooth surfaces, as saprkle from the cornea of the eye, etc. Since gloss is a total reflection of light ultraviolet wavelengths are included. Even the mimic sparkle in the eyespots of butterflies and moth reflects ultraviolet light. Further reading:

Wilbrandt J, Blut C, Girgel E, Fels D, Lunau K (2011) Glanz in falschen Augen – UV-Reflexion und Schutzwirkung von Augenflecken auf den Flügeln von Schmetterlingen [Sparkle in False Eyes – UV-Reflection and Protective Effect of Eyespots on the Wings of Lepidoptera). Entomologie heute 23: 103-116.

The part of one figure of the former paper ist attached: Caligo brasiliensis displaying UV-reflecting crescent mimic sparkle in the eyespots.

Blut C, Wilbrandt J, Fels D, Girgel EI, Lunau K (2012) The ‘sparkle’ in fake eyes – the protective effect of mimic eyespots in Lepidoptera. Entomologia experimentalis et applicata 143: 231-244.

Blut C, Lunau K (2015) Effects of lepidopteran eyespot components on the deterrence of predatory birds. Behaviour 152: 1481-1505.

Some flower-dwelling spiders reflect UV. Herberstein and her colleagues have done quite a bit of work investigating UV reflectance in Thomisus spectabilis, an Australian crab spider. Below is a paper that references the many other UV-related papers that Herberstein's lab has produced.

Herberstein ME, Heiling AM, Cheng K. 2009. Evidence for UV-based sensory exploitation in Australian but not European crab spiders. Evolutionary Ecology 23: 621-634.

Also, some orb-weaving spiders decorate their webs with swathes of silk called stabilimenta. Silk used in stabilimenta is UV reflective.

Craig CL, Bernard GD. 1990. Insect attraction to ultraviolet-reflecting spider webs and web decorations. Ecology 71: 616-623.

Blackledge TA, Wenzel JW. 2000. The evolution of cryptic spider silk: a behavioral test. Behavioral Ecology 11: 142-145.

There may not be a special reason for seeing light in the UV-range for the animals which see it. The only difference between UV-light and visible light is, that we do not see it. The range of light is bigger than the range of our human senses, even in the opposite way to infrared. Is there a reason for humans for seeing red colours and bees do not? This excludes not, that many animals which see UV light use this to their benefit, but it is no must.

Best regards

Rudolf Ritt

Thank you all for your answers!

In some Hypolimnas butterflies, the big white forewing spots are surrounded by an iridescent (interference) area which appears to m and I guess everyone else  to be deep purple: but looking at it is uncomfortable, as if it is on the edge of my visual range. This suggests to me that the main reflecting spectrum is in the ultraviolet, and the human cones are picking up only the tail of the distribution. An analogy is the sqeaking of some small mammals like shrews and (communication squeaks) bats, which is pitched somewhere up at the top of the sensory range: one does not so much sense that one is hearing something so much as "feeling" it!

There is a lot of work scattered in the literature on the appearance of butterflies in the UV. Some early work in the 1950s by Jocelyn Crane or maybe others at the New York Zoological Society station in Trinidad comes to mind: the underside of the red bands in Heliconius is covered with white scales, which are strongly UV reflecting.

I would like to recommend 3 papers with sophisticated studies of the meaning of UV-patterns in a lycaenid butterfly which can be guessed already by the titles:

Knüttel, H; Fiedler, K: Hostplant derived variation in ultraviolet wing patterns influences mate selection of male butterflies, Journal of Experimental Biology, 204, 2447-2459 (2001)

Knüttel, H; Fiedler, K: On the use of UV photography and UV wing patterns in butterfly morphology and taxonomy, J. Lepid. Soc., 54, 137-144 (2001)

Burghardt, F; Knüttel, H; Becker, M; Fiedler, K: Flavonoid wing pigments increase attractiveness of female common blue (Polyommatus icarus) butterflies to mate-searching males, Naturwissenschaften, 87, 304-307 (2000)

Regarding fluorescence in scorpions and other arachnids, I would like to point out that beta-carboline-3-carboxylic acid, a tryptophan derivative, has been identified as one of the molecules responsible for the fluorescence of the scorpion´s cuticle, which may also be associated with hardening of the exoeskeleton. You may check this finding in the original reference:

Stachel SJ, Stockwell SA, Van Vranken DL.The fluorescence of scorpions and cataractogenesis. Chem Biol. 6(8):531-539 (1999)

Hello Bruce

Your question is a very interesting one and I for one would be interested in seeing how your library grows as you gather the information. I myself have investigated reflection of ultraviolet radiation in the built environment. The area is rather limited with little research behind it,  but if you are interested, at the time of completing my PhD I had tabulated what published research there was (at the time) about reflection from terrestrial surfaces (both natural and built). This includes natural surfaces such as sand, earth, water, grass etc. You can find the thesis here: http://eprints.usq.edu.au/19645/  should you wish to explore in that area, although by what you have indicated that's not necessarily your primary focus.

Best regards

Joanna

http://eprints.usq.edu.au/19645/

Thank you all!