Friday, 18 December 2015

How many Hues does it take?

This post follows from one by my friend Ian Fraser in which he considers animals with many colours.  He bases his post on species where many colours is " ...defined as having at least three evident colours without counting black, grey, white or brown ...".  He notes that this is arbitrary but I think it is as good a basis for discussion as any other.  Towards the end of his post he notes that when examining invertebrates he couldn't come up with many examples and none from Australia.

I took this as a challenge. As it was rather warm outside and thus better to sit at a computer (hmmm - thereby adding to heat indoors) I have scrolled through a bunch of my blogposts looking at images of invertebrates to see if I could find examples of invertebrates which met Ian's definition.

This gave me quite a deal of entertainment, including of course the pleasure of revisiting some of the burbles I have done in the past.

A first issue is how many colours are there?  This colour hexagon from EXCEL gives an idea of the range:
I think there are about 120 cells in the hexagon, but I can't work out how to describe them in text.  (Obviously one could do so by defining proportions of red, blue and yellow - or, as IT folk quite reasonably say, magenta, cyan and yellow - but even keeping the proportions to whole percentages that gives 1,000,000 combinations and really needs a large dose of OCD.)  I ended up with effectively a broad rainbow (Red, Orange, Yellow, Green, Blue and Purple - I really can't tell the difference between Indigo and Violet as used in the classic spectrum so have combined them to Purple).

As I had a feeling that butterflies offered a good chance of encountering multiple colours I searched my blog for the word butterfly.  This gave me a list of 45 posts, many of which also had invertebrates other than butterflies.  I decided to stop after I had come up with 50 entities - probably attempting to disprove my possession of aforementioned mental condition.

Of the entities, 15 were beetles, 12 were butterflies (astonishing how many images of Common Browns (Heteronympha merope) I have got - here's one of them).
The other families are in lesser numbers.

In terms of colours identified black was the most common ....

.. and I didn't code anything to purple, which surprises me.  Black and white was quite common , although this Pintail Beetle (Hoshihananomia leucosticta) ...
.. was slightly unusual in being bichromatic.

Of course there are many occasions on which it is difficult to determine which label to attach to a colour: in the Common Brown above is the colour close to the body light brown or a dull orange?  There are also cases where I am really not sure how to code a colour, of which this leaf beetle (Paropsisterna variicollis) ..
.. is an example.  Is it green or yellow?  I concluded it was both!

In other cases such as this Spotted Jezebel (Delia aganippe) there are good solid primary colours of red and yellow as well as the black and white.
I eventually found a beastie which I felt met the conditions as stated.  This is the Crimson Tiger Moth (Spilosoma curvata)  ....
which I felt had a red abdomen, yellow wings and orange hair on the thorax.

Of course, others may feel that the distinction between the upper and lower surfaces of the wings is rather fine, and that the colour of the thorax is merely a step further along the continuum.  A fair call, although when using a function in Photoshop Elements which selects pixcels of the same colour (defined by the program using proportions of the primary colours) the tolerance ;level has to be set at 90% to get all areas selected simultaneously.  With the tolerance set at 50% the three main areas all react differently.

That endeavour has led me to add a little to Ian's definition in that there should be at least one colour from the group {red, yellow orange} and one from {blue green purple}.  Initially I didn't find an image of anything that satisfies this broader definition.  The closest is the Red and Blue Beetle Dicranolaius bellulus:
It does however fail the three colours element!  The search will continue (what is it about OCD I don't understand?)

Possibly a better specimen is offered by the leaf beetle Polysastra costatipennis.
Here we have an orange thorax, green wing cases and a yellow abdomen.  The only area of doubt is that I have another image of what I am sure is the same species, with a much yellower (ie less orange) thorax: that specimen isn't working as hard as this pair seem to be, so perhaps the deeper colour is evidence of something hormonal!

2 comments:

Ian Fraser said...

I am impressed - nay, awed - at both the high degree of development of your OCD, and your stock of spare time! I'm glad though that you didn't find too many easy examples where I failed to find any.

Flabmeister said...

I would have to say that I am equally impressed at the speed with which you read, and proffered a comment on, the post. I suspect you weren't sitting at a terminal waiting for my latest manifestation to arrive!

Much of my spare time arose between being awoken by a noisy magpie at 0430 and taking Tammy for a walk at 0700!

Martin