Xylota tarda?

[JRsbugs]

What sayeth anyone?

Janet

[Dogghound]

Xylota Tarda & segnis are seperated by hair structure on the underside of the hind femora.

X.segnis = has two rows of well separated spines (which are quite long)

X.tarda = has unarranged spines under the femora

All I can suggest is either try and blow up the formora, or if you have any other shots have a good look at them or leave it as Xylota.

On another note it is much more likely to be X.segnis on the basis that X.tarda is quite rare and very local. It is restricted to mature woodland in south and central England. X.segnis is much more widespread and has less specific habitat requirements not as restricted to trees as the other species and is found in parks, farmland along hedgerows, woodland etc.

[JRsbugs]

Lol Dogg, I thought you had that the wrong way around, glad to see you edited it!

I had at first named this X. segnis, as it is one I have. A second look at it started a niggle in my mind that it didn't quite look right for that so I checked what others we have here, I have had X. sylvarum as well.

I have done a lot of research on this one, there is very little about X. tarda but I did find out about the hind femora bristles. I have looked carefully, at first I thought I could see white hairs on the hind femora but on closer insepction it looks like a white patch with white hairs. I have found a couple of pics showing this on a female, if they are correctly identified.

I have also found a female without that white patch, looking at the one on fugleognatur.dk the abdomen shape looks very similar, and the colour band on T2&3 is more orange red than orange yellow as seen on X. segnis., which I have read somewhere. Notice the reddish area on the hind tibia also, which mine has and I haven't seen on X. segnis.

Krat-træsvirreflue (Xylota tarda) - Foto/billede fra Pandrup taget af Emil Lütken - Fugleognatur.dk

On this site there is a female showing white on the hind femora, but the name is slightly wrong (X. tardens), and I know at least one other syrphid on there is incorrect. That doesn't alter the look of the fly though!

http://www.johnsbooks.org/galleries/folder1/page1zm.htm

There's pics of a female at the bottom of this site, for ID with a ? X. tarda which also looks to have white on the hind femora.

Hoverflies

If only I could find the other site, a Scandinavina one which translated by google seemed to mention the white on the hind femora but it seems to have disappeared! It did mention the more orange red band.

This is the only pic I got, it flew quickly. I do have the sort of habitat mentioned for X. tarda, old woodlands, dead wood, stream, etc.

[JRsbugs]

I found the description, it's a Wiki Norwegian translated. The pic when enalarged has X. segnis above it, but I imagine the description has been done by someone who knows.

Google Translate

A medium-sized (9-13 mm), slender flower flies, very short hair, black body except the abdomen second and third paragraph, which is orange red. Den kjennes fra lignende arter på bakbeinas farge: lårene helt svarte, leggene hvite i den innerste tredjedelen, svarte i de ytterste to tredjedelene, føttene gulhvite bortsett fra det ytterste leddet som er svart. The distinguished from similar species on their hind legs color: thighs completely black, white legs in the inner third, replied in the outer two thirds, feet pale yellow except the outermost joint which is black. De ligner sterkt på vanlig vedblomsterflue ( Xylota segnis ) men skiller seg fra denne ved de hvite bakføttene. They strongly resemble normal vedblomsterflue (Xylota segnis) but differs from that of the white bakføttene. Ansiktet er litt uthulet under antennene, som er mørke med det tredje leddet nesten sirkelrundt. His face is slightly hollowed below the antennas, which are dark with the third joint nearly circular. Thorax er tydelig lengre enn bred, ikke påfallende hårete. Thorax is clearly longer than broad, not conspicuously hairy. Bakkroppen er parallellsidig, det første, fjerde og femte leddet er svarte, det andre og tredje leddet nesten helt oransjerøde (ikke skarpt røde). Abdomen is parallellsidig, the first, fourth and fifth link is black, the second and third joint almost entirely orange-red (not bright red). Beina er svarte og gulhvite, baklårene noe fortykket. The legs are black and yellow, slightly thickened baklårene. Vingene er glassklare med brunt vingemerke. The wings are clear glass with brown wing mark.

Copying the text seems to put both languages, but the English parts are in between.

[JRsbugs]

I've got a key for Xylota, just checked it out. I can't see some of which is mentioned but other parts fit X. tarda.

For a start, for X. segnis it states:

Baso-ventral ridge on hind tibiae covered with a row of short, black spines; femur 3 ventrally with widely separated, long bristles on its top half, in addition to scattered black bristles -> Xylota segnis

I can't really see the hind tibia well enough, the one on the left of the fly is more focused and with blowing it up I think I can see some short black spines sticking out the bottom edge of the tibia.

That would then rely on having the bristles also on the femur as described, and in pics I'm seeing of X. segnis these are quite distincitve. I can't see anything that distinctive on my fly. I can see some bristles on the other side hind femur sticking out at the bottom, they don't look very long but it's not the best view either.

One of the lead up keys to X. tarda says:

hind tibiae yellow only at the base; hind basitarsi dark brown/black (except in X. triangularis female)

Looking at the other side hind tibia in focus, there is yellow as the base (adjoining the femur) but I can also see some yellow past the black at the other end. However, the other option in that section states "Hind tibiae widely yellow at both ends: hind basitarsi (and two succeeding tarsal segments) yellow" for a species we don't have so I would follow that option.

Which brings me to:

Anterior anepisternite 1 with most of surface undusted, brightly shining

OR

Anterior anepisternite with either entire surface, or most of surface dull, dusted

I found out where that part is, somewhere above the coxa, but I can't pick it out in my pics.

If I take the first option, it takes me to:

Abdominal tergite 3 with a transverse, orange band across anterior half of the tergite; hind femora with middle third of ventral surface covered in black, spiny hairs -> Xylota tarda

I can't see if the middle third of the ventral surface of the hind femora is covered in black, spiny hairs either!

However, if I took the alternate option it leads to either a species we don't have, or another which doesn't fit the abdomen colouring.

There is the dark brown hind basitarsi with yellow at the base of the tibia which does fit, I think!

[Jason Green]

Afternoon Janet,

How about next time, you try what PeterBolson does; pop one in the fridge for a while, get the images you need of the ventral view of the hind femora (simplicity itself, I'd have thought! ) and then release it alive? I'd have liked to have known more conclusively what it is too - but on the face of it I have to think along the lines of segnis as well.

How do you get to see so many of these nice Xylota spp.? I only get to see the back-end...

Take care,

Jason

[JRsbugs]

Originally Posted by Jason Green

Afternoon Janet,

How about next time, you try what PeterBolson does; pop one in the fridge for a while, get the images you need of the ventral view of the hind femora (simplicity itself, I'd have thought! ) and then release it alive? I'd have liked to have known more conclusively what it is too - but on the face of it I have to think along the lines of segnis as well.

How do you get to see so many of these nice Xylota spp.? I only get to see the back-end...

Take care,

Jason

Jason, for a start, if I had tried to nab the thing I would have got nothing, the pic I got was a quick one after it had landed, then it took off.

As far as being X. segnis goes, show me one which has brown hind basitarsi.

I get them because I am quick off the mark, sharp shooter JR.

[Geoff F]

Surely the visual starting point for separating segnis and tarda are the short black marks on the abdomen at the start of the orange area. Narrow for X. segnis and wider for X. tarda.

X. segnis has a parallel sided abdomen while X. tarda is slightly 'pear shaped'.

So even without using any keys, I would say X. tarda here.

[JRsbugs]

I haven't seen the pear shaped abdomen mentioned Geoff, I guess it's in your book which is obviously a necessity! That was one thing which I thought looked different too, apart from the brown hind basitarsi.