Hoverfly ID's

[Tormentil]

Can some one ID these hoverflies, please.

1.

2.

3.

4.

[JRsbugs]

Nice pics!

#1 Platycheirus albimanus male as it appears to have swollen white front tarsi.
#2 could be a melanic Melanostoma, the bright green halter would suggest M. scalare but others can have green halters too, maybe not so bright but I can't be certain. I know M. mellinum females are more likely to be melanic but yours is a male.
#3 Syrphus ribesii female which has all yellow hind femora.
#4 same as #3.

All above from my basic knowledge only, someone else may know more!

Janet

[Jason Green]

Hi Tormentil,

Regarding 3+4...

Diptera > Syrphidae > Syrphus ribesii (S. ribesii) - No Common Name

[A Hoverfly]

Here's Why

• Pale scutellum
• Broken band on first ternite, rounder than that of E. grossularie...
• Yellow-black, darkening hind legs
• Dense, short orange thoracic hairs

Sexing
It's a girl, too. Note the gap between the eyes...

1. Eyes close = Chap
2. Eyes far apart = Female

...get it

Take care,

Jason

[JRsbugs]

There's 4 species of Syrphus which are very difficult to separate. The first port of call to identify them is the hind femora, after that there are more features which have to be taken into account.

Syrphus ribesii female - hind femora all yellow or with a little black at the base.
S. ribesii male - hind femur either yellow or black on basal two-thirds. If there are hairs on the eyes it is S. torvus, males having more than females but apparently some other species can have some hairs too.

Syrphus vitripennis more difficult, with yellow bands on tergites 3 and 4 complete as a general rule, where in S. ribesii they can be slightly broken.

Males of S vitripennis have yellow apical quarter of hind femora yellow. (Males of S. ribesii have hind femora either all yellow, or black on basal two-thirds.)

Female S. vitripennis difficult to separate from S. rectus, if the front and middle femora have pale hairs on the apical quarter and it is bare eyed it is S. vitripennis.

Male S. vitripennis are indistinguishable from male S. rectus.

Apart from all that, if you can study their wings under a microscope you may be more successful in separating male S. vitripennis and S. ribesii males if in doubt. S. ribesii has the bm cell with a small patch devoid of tiny hairs, but that doesn't stop S. vitripennis from being indistinguishable from male S. rectus. In the absence of using a microscope, and not being able to assess how much of the hind femora is black, then if the bands are slightly broken then it will most likely be S. ribesii.

[Tormentil]

Gee whiz ! Thanks Janet, Jason & JRsbugs, especially for the detailed explanations. We learn a little more every day.

Santa should be bringing me Stubbs & Falks "Hoverflies of Britain", so I might even learn a little more about these fascinating insects.

If any other WABers are, like me, a bit baffled by the anatomical terms, here's a wee help......




p.s. Apical, from the Latin apex (plural apices) meaning to be at the apex or tip

[Jason Green]

Pleasure

Yes, good anatomical images there - I use them too

[Dogghound]

Originally Posted by JRsbugs

#1 Platycheirus albimanus male as it appears to have swollen white front tarsi.

All male Platycheirus have enlarged tibiae, ID features are the hair structure on the middle coxae is usually a good way to tell species apart. I agree with P.albimanus on this one.

I would leave 2 as Melanostoma sp, as you need to see the size of the plates on the side of the thorax which arnt clear in the photo.

I agree the last two are S.ribesii

[JRsbugs]

Originally Posted by Dogghound

All male Platycheirus have enlarged tibiae, ID features are the hair structure on the middle coxae is usually a good way to tell species apart. I agree with P.albimanus on this one.

I would leave 2 as Melanostoma sp, as you need to see the size of the plates on the side of the thorax which arnt clear in the photo.

I agree the last two are S.ribesii

Good to know I got them correct! I had meant to add the note about P. albimanus re others having enlarged tibiae, but it is only the males I believe which have white front tarsi/tibiae? The finer details I have yet to learn!

There's a new term to add to your diagram Tormentil, coxae which I believe is the part which joins the leg to the body, and in this case it is the middle leg being referred to? I think P.albimanus is also the most common?

I really have to get a macro lens in order to be able to see these details.

[Dogghound]

Originally Posted by JRsbugs

Good to know I got them correct! I had meant to add the note about P. albimanus re others having enlarged tibiae, but it is only the males I believe which have white front tarsi/tibiae? The finer details I have yet to learn!

There's a new term to add to your diagram Tormentil, coxae which I believe is the part which joins the leg to the body, and in this case it is the middle leg being referred to? I think P.albimanus is also the most common?

I really have to get a macro lens in order to be able to see these details.

Yes only males have the enlarged white tibiae. The coaxe is the first segment of the leg joining it to the body. I agree I need a macro too , I often use a microscope but this involves dead specimens I would rather this not be the case but If its recording then its often the only way with some species.