Charles T. Faulkner (ctfaulkn at utkvx.utk.edu) wrote:
: In the original post on Bionet.general
: >>> colinc at cix.compulink.co.uk ("Colin Cracknell") wrote:
: >>> As a child I used to wonder why big fat flies were known as bluebottles,
: >>> when they were black. As time went on, I saw occasional blue ones, but
: >> on their wings. I understand that these scales polarize light.
: This sounds reasonable to me. I wonder if we can get the expert opinion of
: an Entomologist to set us straight ?
I passed the message on to an former student of ours, who is an
entomology grad student at Iowa State and he sent the following response
which seemed to make sense (what do I know, I am a Carboniferous
paleoecologist that teaches Zoology).
To: James Mahaffy <mahaffy at dordt.edu>
From: jvandyk at iastate.edu
Subject: Re: pigment in blue bottle files (fwd)
>> >> The pigment may not be a pigment after all. Many butterflies have
>> >> similar metallic sheens, but this is caused by the scales
>> >> on their wings. I understand that these scales polarize light.
>> >> Of course this could be completely wrong!
>>>> This sounds reasonable to me. I wonder if we can get the expert opinion of
>> an Entomologist to set us straight ?
I'm not sure about the "expert" part, but:
Colors in insects are produced by light reflected from the cuticle. Two
ways of producing color are recognized: those due to the
physical/structural nature of the cuticle and those due to presence/absence
of certain pigments such as carotenoids, tetrapyrroles and quinones.
So-called "physical" coloration can be due to light scattering,
diffraction, or interference. Many butterflies achieve their striking
coloration through interference.
There are also many species of Calliphoridae, so different coloration is to
be expected when observing at your local compost pile or back alley.
However, even within species color can differ. Consider this description of
the Black Blow Fly (Phormia regina) from Bland & Jacques "How to Know the
"...bluish black, greenish black, or blue-green;..."
John VanDyk, Medical Entomology ( Internet: jvandyk at iastate.edu
436 Science II FAX: 515-294-5957 )
Iowa State University, Ames, IA 50011 (USA)
James F. Mahaffy e-mail: mahaffy at dordt.edu
Biology Department phone: 712 722-6279
Dordt College FAX 712 722-1198
Sioux Center, Iowa 51250