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#1 2017-09-12 11:37:49

Gateside
DF Members
Name: Nigel Gilligan
From: Cumbria
Registered: 2011-08-26
Posts: 906

Red-eyed fruit fly - is this Geomyza hackmani?

Using the key to Opomyzidae by CM Drake.

Looks like a Geomyza species.

From several images, ratio of wing width / length = varies between 0.24 & 0.28
Structurally, it looks like a male from the rear of the abdomen.
Estimated body length between 4 & 5 mm.

From the location and intensity of the spots, plus the long narrow wings, it can only be either G.balachowskyi or hackmani

The postnotum (I have never seen this term used before!) has a darker strip arcing around the rear edge and sides. This better matches the colour of most of the abdomen (except the front half of the first tergite) , than the rest of the thorax. This indicates hackmani.

There is also a subtle difference in the illustrated venation, in that hackmani has the rear, more strongly darkened cross vein, slightly nearer the end of the 4th cross vein, and this also matches my image.

Without the specimen to check the genitals, is this convincing for Geomyza hackmani?

As an addition, it is consistent with images on Dipterists Info, and
compares very well, especially with the dark postnotal dark stripe, with one here:
http://insectmacros.com/index.php/sobi- … kmani.html

Nigel G


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Last edited by Gateside (2017-09-13 10:40:05)

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#2 2017-09-13 20:54:00

pbrighto
DF Members
Name: Phil Brighton
From: Warrington
Registered: 2011-10-21
Posts: 347

Re: Red-eyed fruit fly - is this Geomyza hackmani?

I am rather confused about the term fruit fly as I used to think it just referred to Drosophilidae.   I have also seen it applied to Tephritidae, but only some of them attack fruit.   I thought Opomyzidae were mainly associated with grasses - that's where they seem to lurk.   "Picture-wing flies" seems a good term to apply to small flies with pretty wings.

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#3 2017-09-13 23:48:58

Gateside
DF Members
Name: Nigel Gilligan
From: Cumbria
Registered: 2011-08-26
Posts: 906

Re: Red-eyed fruit fly - is this Geomyza hackmani?

Yes, you're right, Phil.
I was being sloppy, doing the text without using the proper name. I thought I might get away with it ...

Nigel

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#4 2017-09-15 11:46:14

oxycera
DF Members
Name: John Coldwell
From: Barnsley
Registered: 2008-04-27
Posts: 314

Re: Red-eyed fruit fly - is this Geomyza hackmani?

Hi Nigel,

You may well be correct but as far as I understand it an examination of the male genitalia is necessary (as is so often the case with many
diptera).

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#5 2017-09-15 13:04:40

Gateside
DF Members
Name: Nigel Gilligan
From: Cumbria
Registered: 2011-08-26
Posts: 906

Re: Red-eyed fruit fly - is this Geomyza hackmani?

Hi John

I've just been looking at the intro text, and it says "... keys place strong emphasis on wing pattern and coloration, but relatively little on morphology. However the genitalia , especially of Geomyza, are often distinctive, and their examination is sometimes essential for identification."

... which does not clarify either way!

The couplet for mine, with both balachowskyi and hackmani, does mention both the surstylar lobes for both, and the colour difference. It doesn't mention the subtle difference in wing venation.

I would give mine 1.5+ out of a possible score of 2. Is that enough?!

I shall submit it, and leave it up to the decision maker.

Nigel G.

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#6 2017-09-21 12:18:22

AliCullaloe
DF Members
Name: Array Array
Registered: 2014-08-20
Posts: 56

Re: Red-eyed fruit fly - is this Geomyza hackmani?

hi Nigel

How does one come by that key? Is it available on paper or is there an electronic copy floating around the ether?

Cheers
Ali

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#7 2017-09-26 15:06:12

Gateside
DF Members
Name: Nigel Gilligan
From: Cumbria
Registered: 2011-08-26
Posts: 906

Re: Red-eyed fruit fly - is this Geomyza hackmani?

I cannot remember where I got it from.
However, by searching the net, I found this link to a photocopy of it.

http://biostor.org/reference/129772

Nigel.

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