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Most users ever online was 248 on Wed Dec 12, 2007 11:53 pm


Poss Helophilus pendulus

 
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Simon R



Joined: 12 Jul 2006
Posts: 34
Location: Jersey, Channel Islands. U.K.

PostPosted: Sun Sep 23, 2007 6:26 pm    Post subject: Poss Helophilus pendulus Reply with quote

Found dead Sad this morning in a friends greenhouse, I was a bit confused about the eyes Confused until using a hand lens discovered it was just dew Embarassed

Si
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John O'Sullivan



Joined: 05 Oct 2005
Posts: 128
Location: Sandy, Bedfordshire, UK

PostPosted: Sun Sep 23, 2007 9:03 pm    Post subject: Reply with quote

Well, as this one isn't going anywhere, Simon, you have a chance to take a good look.

The key feature with the commoner Helophilus is the hind tibia. If it is mostly yellow, with black only covering about the third furthest from the body, then it is H. pendulus. If it is more than half black, then it is likely to be hybridus. Also, male hybridus are more yellow on the upper abdomen, with continuous yellow at the sides joining the top patches of yellow to the middle patches. Unlike many other hoverflies, the males' eyes don't touch in Helophilus, and the best way to determine the sex is to look at the underside of the tip of the abdomen, where the male sex organs show a certain complexity and form a slight but distinct bulge, whereas females come to a gradual point. Which is your specimen?

While you are looking, you might like to check the face; another fairly likely Helophilus to be found is trivittatus. In both sexes this has a yellow face; the two mentioned above have a strong, black stripe down the middle of the face.

If you think that hoverflies are going to be your thing, then you are going to need British Hoverflies, by Stubbs and Falk. If you don't know about it already, see earlier posts for details. If I remember right, you live on the Channel Islands, so, who knows, you might find some mainland European species that we don't get in Great Britain. Happy hunting!

John
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Simon R



Joined: 12 Jul 2006
Posts: 34
Location: Jersey, Channel Islands. U.K.

PostPosted: Mon Sep 24, 2007 4:02 pm    Post subject: Thanks Reply with quote

British Hoverflies on its way Very Happy do you use a microscope for the really minute detail if so which one. Confused I have a Ruper10x20x. Not easy in the field even when caught in a pot.

Regards

Simon
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conopid



Joined: 03 Sep 2005
Posts: 342
Location: Shrewsbury, Shropshire

PostPosted: Mon Sep 24, 2007 8:56 pm    Post subject: Reply with quote

A stereoscopic microscope with 20 x magnification will suffice for most hoverflies, but I find 30- 35 x is useful for smaller features like the pits on the tarsal segments of some Platycheirus and the microtrichia on wings of some Syrphinae. I actually use 64x occasionally for really difficult features.

Learn from my mistakes and don't buy a microscope without taking lots of advice. There are some good deals out there, but also some bad ones. Lighting is also an important consideration. I recently used a quite cheap (still costs hundreds of pounds though) microscope at the Field Studies Centre and it was a remarkably good instrument, so be sure to try before you buy. Really top quality microscopes can set you back a LOT of money, but if you shop around you should be able to get a good compromise between quality and ££. Others am I sure will advise their experience.

This firm http://www.gxmicroscopes.com/html/stereo.html seem to offer well priced microscopes. I think this is the brand I tried at the Field Studies Centre, but I am not 100% sure on that. Can others comment on GX Microscopes?

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Nigel Jones
Shrewsbury
Shropshire
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lauriek



Joined: 07 Aug 2007
Posts: 29
Location: Kent

PostPosted: Mon Sep 24, 2007 9:36 pm    Post subject: Reply with quote

The Trekker is a nice portable microscope, but I haven't personally used one for bugs yet... (apart from bug eggs). Just google trekker microscope to find out more! It is 35x magnification, or 10x if you pull out the eyepiece and use that as a loupe.
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John O'Sullivan



Joined: 05 Oct 2005
Posts: 128
Location: Sandy, Bedfordshire, UK

PostPosted: Wed Sep 26, 2007 7:26 pm    Post subject: Reply with quote

Conopid is quite right about the need to take advice, and I agree with his thoughts on magnification sizes: I also use 10x and 15x quite a lot. It's a bit frustrating that we can't buy microscopes like we can telescopes, by going to a dealer and comparing several brands and models. Instead, I suppose many of us take a chance and get one by mail order; it then obviously makes sense to be sure you can easily return it, if it's not what you want. The web should help, and I'd recommend the websites of Brunel Microscopes and Lakeland Microscopes (both easily Googled). They give telephone numbers and I'm sure staff would be happy to advise. My first microscope was a basic but optically good stereo from Brunel. Working room between the lens and the specimen is important; this had loads, and I got on well with it for several years. I then began to feel that a zoom would be an advantage, and I bought a zoom stereo from Lakeland, which I really like; the zoom really is a major convenience. Neither of my microscopes was expensive, and although I occasionally think about a big name brand, costing thousands, I'm not sure most of us really need such fabulous optics for our general hoverfly studies. As to lighting, my Lakeland model has a built in light, but I always supplement it with a bright table lamp which can be brought close to the specimen; it's effective, and much cheaper than fancy specialist lights. No doubt the latter have their uses, for instance for examining delicate living creatures without cooking them! As long as I'm careful not to keep live flies under the lamp for too long, it seems to do them no harm. Dead material is not affected at all. Well, we all have our favourite kit and develop our own tricks to use them, and I'm sure that Simon will find his. By the way, Simon, what you are using to hold your specimens while examining them with your Ruper? You've no doubt worked out that clean glass is much better optically than plastic; and the tube or pot should never be so wide that a fly can be out of focusing range. After that, it's just practice and patience!
That's quite enough from me for now. Have fun.
John
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Simon R



Joined: 12 Jul 2006
Posts: 34
Location: Jersey, Channel Islands. U.K.

PostPosted: Fri Sep 28, 2007 2:17 pm    Post subject: Thanks Reply with quote

A big thank you to you all for your time, Very Happy Stubbs and Falk should be arriving soon, a zoom microscope looks the best bet as I am also very interested in spiders Shocked ect.

Itís very difficult to buy anything like this in Jersey so itís a case of trial and error. Evil or Very Mad

Thanks again for all your help Laughing

Simon
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