h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Cool Malabarista - or is it? Darn it, we have competitors!

It took my brain a little while to dredge this up - but I eventually remembered that bees look for patterns visible in Ultra violet light to guide them to the pollen and nectar they seek.

The scent helps, but apparently yellow flowers show up these bee 'landing-guides- easier than red coloured flowers.

http://answers.yahoo.com/question/index?qid=20100425113621AAXXlzz


I suppose bees need to find flowers quickly in the Spring - when food sources for them are limited, and the yellow helps the bees. There are less pollinating insects about anyway in the Spring, so the flowers may be competing for pollinators?

But blue should be more visible in Ultra-Violet than yellow is.

only if the human visible blue pigment is the only pigment in there.
If the yellow flowers have UV pigment as well, then we as humans wouldn't see it but the bees would.

That doesn't explain why they are yellow. What Lanzababy is saying is that the flowers are a combination of yellow and an invisible colour which the bees can see and the bees are attracted to the invisible colour. But they could just as easily be red plus the invisible colour, or blue plus the invisible colour.

But it wasn't intended to. It was intended to rebut your point that yellow is not a good UV colour by saying there could be more than one pigment present.

Why yellow + UV is a different question. Of course, if bees (and other pollinators) can see a wider range than just UV then Yellow + UV would stand out a lot in spring woodlands.
Certainly more so than just UV, or blue+UV.

If I remember rightly, bees can see from orange to ultraviolet and all the colours in between, but not red.

so yellow+UV would stand out a lot for them then?

Still, since they're all dying off I guess they're less of a selective pressure for flowers atm.

Apparently bumble bees like to make their nests in old mouse holes. If you have an old teapot, you were going to throw out, you can bury it with the spout just level with the soil surface to make a suitable bee home.

It seems to me there's some major principles being missed in the subject of spectroscopy here.

Pigments absorb radiation of all varieties and (normally) re-emit radiation in a variety of frequencies. These frequencies are quantised - not on a sliding scale, and are directly linked to the quantum electron promotion that happens when radiation is absorbed. It's a basic tenet of atomic science that electron energy levels are quantised - hence the electron orbitals that we were hammered with at GCSE. The therefore a statement like: "But blue should be more visible in Ultra-Violet than yellow is." (translated as "the wavelength of blue light is shorter than that of yellow light, and therefore closer to ultra-violet") meaningless.

Any basic spectroscope will show you a pattern of distinct emission lines in a wide range of the spectrum. For example, a classic red sodium flame will also show clear lines in the blue and green parts of the spectrum. So it's simply not enough to compare a yellow plant to a blue plant in terms of light emission. I agree that yellow plant pigments probably emit radiation more detectable to bees, but the degree of emission, and bees sensitivity to radiation, is being grossly understated.

B

Yellow looks like a "bright" colour to us, as far as I can see, because our "red" sensors and "green" sensors overlap very much, so yellow gives a strong signal from both. I've no doubt this is not the case with bees, so yellow flowers should not be any more noticeable to bees than any other colour.

I think the point I was trying to make ( not very successfully ) was that it was the contrast between the yellow background and the ultraviolet landing guides on the petals(invisible to humans) that make the nectar sources easier for the bees to find.

I found some photos of how bees see yellow flowers - well who would have thought that the common dandelion looked like that?

http://www.dailymail.co.uk/sciencetech/article-473897/A-bees-eye-view-How-insects-flowers-differently-us.html

That's very interesting.

Well, when you snap yellow flowers, they absolutly stink. So, couldn't this colour be a warning to animals?