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#1 2015-02-16 00:59:53

Gateside
DF Members
Name: Nigel Gilligan
From: Cumbria
Registered: 2011-08-26
Posts: 932

Muscid (?) with antennae that appear to change colour

I have a long series of photos of this supposed Muscid, as it sat in the bright sunlight on a wall, intermittently rotating, but always with direct sun on its head. The fly started off facing up, then down, then sideways.

I have seen 2 threads related to blowing bubbles, the first one below appears to be a very similar or identical species, supposed at the time to be a Calliphoridae ( and not replied to). I did wonder whether mine was that family, but discounted it on the basis of the dull thorax and abdomen. The venation is very similar to Musca domestica, but the vein M1 has a more extreme bend in my images here.  So maybe it's a close relation, but it's not a  species I have recorded.

http://www.dipteristsforum.org.uk/t4254 … bbles.html
http://www.diptera.info/forum/viewthrea … ad_id=1016

I don't really expect a species name for mine - it doesn't seem to have any notable features, except maybe the venation combined with the red-brown face..

The strange thing which I do wonder about is the antennae, but maybe there is some other simple explanation, and I will now make a complete fool of myself with my theory below! But I would rather make a fool of myself than not share my observations.

When the fly is facing upwards, the antennae are dark brown, with a reddish base. When it turned to face down, the antennae appear to be translucent. Its left one appears to show light from the wall, the right one appears to be somewhat like the colour of the face behind (and it also hangs down more). In all cases the reddish base of the antennae is constant. When the fly rotated itself sideways, the antennae resume their normal appearance, and don't appear translucent - they don't  appear to show the colour behind them.
(and the arista are definitely plumose)

(I have photos showing a bit more of the abdomen from behind, and also face-on views)
Is there another explanation for what I can see? And if not, what is going on here?

Nigel


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Last edited by Gateside (2015-02-16 10:17:42)

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#2 2015-02-16 22:54:15

conopid
DF Members
Name: Nigel Jones
From: Shrewsbury
Registered: 2008-02-27
Posts: 637
Website

Re: Muscid (?) with antennae that appear to change colour

Hi Nigel,
I spy short golden hairs on the thorax, which would make it Pollenia species in the Calliphoridae. It looks to have a jet black abdomen, so might be P. amentaria, but don't take that as a positive ID. P. amentaria is generally a species of uplands and "wild places".

Nigel Jones


Nigel Jones
Shropshire

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#3 2015-02-17 10:35:23

Gateside
DF Members
Name: Nigel Gilligan
From: Cumbria
Registered: 2011-08-26
Posts: 932

Re: Muscid (?) with antennae that appear to change colour

Hi Nigel

So my reasoning for rejecting Calliphoridae was not sound (in all cases). Thanks for the correction.

The first image I loaded before does have a patchwork of paler on the side of the abdomen. I can't make out what that is, but I assume it's caused by short pale hairs. 

I have loaded a new view, this time from the rear. This shows that whilst there are quite long black hairs/bristles on the abdomen (as previous images), there may well also be some shorter pale hairs too.

The thorax looks jet black from the rear angle, but the abdomen actually has a hint of blue, not black. So perhaps that is a pointer to it not being P. amentaria anyway. (though that species is plausible for this locality, being on the edge of a vast upland area, and well away from civilisation.)

Nigel G.


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#4 2015-02-17 12:30:36

ChrisR
Administrator
Name: Chris Raper
From: Reading, UK
Registered: 2008-03-08
Posts: 392
Website

Re: Muscid (?) with antennae that appear to change colour

I'm just wondering whether this is a Calliphora that has been taken at an angle that is making the paler sides look more Pollenia-like than they should be? It's true that the sides look ginger but I am not sure that the hairs are the same as I would expect on a Pollenia and the head shape looks more like Calliphora to me. Pollenia have more of a snub-nose and very long gena. The last shot makes it look much more like Calliphora sp. to me and the bluish gast would fit too smile

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#5 2015-02-17 15:54:10

Howard Bentley
Committee
Name: Howard Bentley
Registered: 2008-07-07
Posts: 743

Re: Muscid (?) with antennae that appear to change colour

I must admit that my first thought was Pollenia, but then I had the same reservations as Chris has expressed, and didn't write a post in consequence. One thing is certain - it ain't no Muscid! A definite Calliphorid of some kind.

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#6 2015-02-17 21:55:10

conopid
DF Members
Name: Nigel Jones
From: Shrewsbury
Registered: 2008-02-27
Posts: 637
Website

Re: Muscid (?) with antennae that appear to change colour

Yes, I too thought the jizz was wrong for Pollenia, but decided some hairs on the thorax were golden, but maybe they are not. The incredible colour shifting fly!

Calliphoridae at least then....


Nigel Jones
Shropshire

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#7 2015-02-17 22:49:30

Gateside
DF Members
Name: Nigel Gilligan
From: Cumbria
Registered: 2011-08-26
Posts: 932

Re: Muscid (?) with antennae that appear to change colour

Thanks for all those comments, the subtlety of which is something I can't really appreciate without the experience!
I did think at the time it would be an unlikely candidate for a definite ID, and in that at least I was right.

However, I did pursue it at the time because of the obvious water droplet aspect, and then realised subsequently that the antennae were behaving oddly. I can't believe that the effect is technical, or some sort of illusion. It is too consistent in various aspects -  such as the sequence of events, the consistent appearance of the effect across the surface of the antennae, and the relationship (and non-relationship) to the background colour of the antennae at each point in time - to be anything other than real (at least that's what I think!).

I see that diptera do have a circulatory system for which there is a vessel down the centre of the antennae, and a sort of heart mechanism in the head, but the stuff I was reading gets a bit too esoteric for my liking as a general numskull. But it does seem possible that what I was seeing was some sort of effect as a consequence of the fly's changing circulation system, which might be related to the purpose of the droplet (and also the digestive system?).

Nigel G.

Last edited by Gateside (2015-02-17 22:51:44)

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