UK Hoverflies (Syrphidae)'s Journal

Hello all,

August was a wet month, but still plenty of Syrphid observations have poured in. The NeedsID pile is taking it's final end-of-season shape, which I'll come onto in a moment.

Updates

The only update to the project content is that I have edited the sexing hoverflies article and associated URLs to include the Subtribe Spheginina as exceptions to the general rule, which I had missed. If you are new to the project, do check out all the content via the index.

Annotations

The proportion of observations annotated in August has dipped a bit from July but remains well ahead of where we were before that. Adding annotations to observations is a great way to get started contributing to iNat and the UK recording scheme. Read the annotations and sexing hoverflies articles if you think you might like to chip in!

Identifications

The pile needing ID has increased in August as should be expected. The only genera to decrease are Episyrphus, Leucozona, Merodon, Rhingia, Volucella and Heringia. The number of observations stuck at higher levels has also decreased which I think is quite remarkable - if you've been involved in that then well done! Perhaps as a result of that a few genera have swelled significantly - most notably Syrphus and Sphaerophoria which are up 10% and 19% respectively in just one month despite being some of the largest to start with!

That's all for now. Enjoy September - next week might be good for late-season hoverating!

(all data compiled on 1-Sep-23)

Sphaerophoria, Syrphus and Eupeodes are three genera that dominate the 'Needs ID' pile in the UK. It is no surprise why: they are commonly observed, and it is frequently impossible to identify the species from photos. The UK Hoverfly Recording Scheme accepts records at the genus level, but these iNat observations will not reach them unless they are made 'Research Grade'. Observations become 'Research Grade' automatically if the ID is confirmed at species level, but at higher levels someone needs to click the box in the DQA section of an observation that reads: "Based on the evidence, can the Community Taxon still be confirmed or improved? No, it's as good as it can be"

Here are a few pointers on using this box:

1) Before making something research grade, check that the annotations have been added.

2) Make sure that the Community taxon is at Genus. (Not just your own ID)

This needs to be fleshed out. The 'Community Taxon' is the one that has the support of the community (i.e. more than 2/3 of at least 2 identifications in agreement). The ID shown on the page is often the leading ID, not the Community ID. For example:

You find an observation with just one ID 'Family Syrphidae', you add the ID 'Genus Syrphus'. Do not click 'No, it's as good as it can be' at this point. The Community ID is still 'Family Syrphidae', because that is what two IDs agree on. If you click at this point it will become a casual observation at Family, rather than a research grade observation at Genus. You need to wait until someone has agreed with your Genus ID.

You can check what the community taxon is on the right hand side on the observation page on the website:

More information about how the Community Taxon works can be found here

3) Only use it if you are confident that the observation cannot be ID'd further (not just that you can't ID it further).

This will be the case only if the necessary ID features are not visible, or the photo is very obscure (too blurred). Of course there is an element of judgement involved, but we can try to be as objective as possible.

I'm aiming to add some specific resources to help with the three genera, Sphaerophoria, Syrphus and Eupeodes sooner or later, but I did make a guide to European Syrphus a while ago where you can get plenty of information already.

Observations of Syrphus build up very quickly on iNat - they are common and usually cannot be identified to species. It is also a genus where it is helpful to ID males and females separately because there are different things to look for - so it's particularly helpful to add the sex to these. I made a key to the European species a while ago and I won't repeat too much of the information there. Everywhere in Europe the main species are S ribesii, vitripennis and torvus, other species are always rare. The aim here is to focus on these three species to help us identify them, and know when an observation should be made Research Grade at Genus level. S nitidifrons has also been recorded in the UK, but you won't confuse it with these three - I'm just ignoring it here, the statements below may not apply to S nitidifrons.

Syrphus usually have:
--a golden dusty coloured scutum (but sometimes can be greyer or shinier)
--Front margin of abdominal bands quite straight and horizontal
--Hind margin of abdominal bands pinched forwards at the sides (and usually in the middle)
--Male frons mostly yellow but with a black mark above the lunule in the middle
--Female frons the same but the black mark is extended in a triangle with its apex close to the black part of the vertex.
--Scutellum is distinctly yellow
--T4 and T5 have narrow yellow hind margins, but T5 itself is not distinctly yellow.
--The face is entirely yellow, without a stripe.
--Dark antennae (not necessarily completely black though)

Distinguishing Syrphus from Parasyrphus

Parasyrphus is the genus most easily confused with Syrphus. Their scutum is usually darker (typically dusted a golden colour in Syrphus), Syrphus usually have a bushier fringe of yellow hair around the scutum too. The legs of Parasyrphus -especially the hind legs - are generally much blacker and the body is typically more slender. The face of Parasyrphus usually has a vertical black stripe down the middle and the frons is typically much darker. Familiarise yourself with the pictures of Parasyrphuson Steven Falk's Flickr page to see these features.

Distinguishing Syrphus from banded Eupeodes

The bands on banded species of Eupeodes are wavier than Syrphus (especially the front edge - having either a 'moustache' appearance or a 'sunglasses' appearance. The scutum is dark and shiny in Eupeodes (typically dusted a golden colour in Syrphus), and the fringe of hairs around the sides of the abdomen (except T2) is black rather than yellow.

Distinguishing Syrphus from banded Epistrophe

Epistrophe also usually have a face stripe and a dark shiny scutum. The bands on most banded Epistrophe are particularly straight - they may have a dink in the middle of the hind margin, but they meet the edge of the abdomen almost at full width. Several species have distinctly orange antennae and the frons is usually different. The most Syrphus-like species is E grossulariae, where the female also has a dark triangle on the fron - but the antennae are deep black and the frons triangle reaches all the way to the antennae - not just the top of the lunule as in Syrphus.

Identifying UK Syrphus species

A general scheme for identifying UK Syrphus looks like this:

(Coverage of microtrichia on the 2nd basal cell of the wing (incomplete in vitripennis, complete in the others) and the colour of bristles/hairs on the knees (yellow hairs in vitripennis, black bristles in the others) can also be used for ID but are basically never visible in photos).

This seems fairly simple but it's worth giving a few more pointers:

Identifying Syrphus ribesii in photos

Male S ribesii are not identifiable from normal photographs, because they cannot be distinguished reliably from S vitripennis. However typically S ribesii males have the hind femur 1/3 - 1/2 yellow, whereas S vitripennis have it only 1/5-1/4 yellow. If the hind femur is very yellow, you may rarely find some people (especially from overseas) identifying the species on that basis. HRS will not accept the record at species, but personally I am not inclined to disagree on iNat where this happens. Leave it be - the recording scheme can decide what they want to accept.

For female S. ribesii you need to be confident that you can see at least half of the hind femur to be sure it doesn't go black. Beware: the abdomen is fringed with yellow hairs, so if you are looking down from above through these hairs, they can obscure the colour change making you think that the femur remains yellow for longer than it does. Colour can also be hard to judge through the wing if there is glare.

Identifying Syrphus torvus in photos

The key thing to realise about S torvus is that the eye hairs are much more obvious in males than females. In males you can often see the eye hairs as a 'halo' around the eye, even in pictures that are not especially sharp. Females are a different ball game - it takes a very clear picture to be sure that there are hairs - they are both shorter and sparser than the males' eye hairs.

S torvus, especially females, also tend to have a bit of a different 'jizz' to the others - typically a bit darker than other Syrphus with narrower bands and a darker wing stigma. That alone is not a basis for an ID though.

Identifying Syrphus vitripennis in photos

For male S vitripennis see comments on male S ribesii above. Some people, especially from continental Europe, will ID this species if the hind femur is only very narrowly yellow - but HRS will not accept such records.

Identifying female S vitripennis is also extremely difficult because you have to be sure that eye hairs are absent. Given how hard these are to see on a female torvus, it is even harder to prove the negative! Some workers will ID a female S vitripennis if the eyes are visible sufficiently clearly to see the ommatidia over a significant area of the eye but HRS will still not accept such records - for their own database they will record it as 'Genus Syrphus'.

So when is it safe to make an observation research grade at genus?

It should be safe to make an observation research grade at genus if microscopic features of the knee hairs/bristles or the wing microtrichia are not visible and

1) It's a male and hairs are not visible on the eyes

2) It's a female, no hairs are visible on the eyes but it's not an exceptionally clear picture of the eyes, and either the hind femur is only visible for less than the apical half or the hind femur is partly black.

If you're not sure of your judgement, there is never any harm in leaving it to someone else!

Continuing this little series on the neediest hoverfly genera, we come to Sphaerophoria. Another genus that is frequently observed but often unidentifiable.

Only 'two and a half' of the UK's 11 species are typically identifiable in photos: S loewi, S rueppellii and male S scripta. Thankfully S scripta is by far the commonest species, so a lot of males can be identified.

There is also an observation field called 'Sphaerophoria identifiable group', which Caleb Scholtens produced to help categorise the North American species. I asked him to add some values useful for European species, which he kindly did. You might want to use this because it makes it possible to search for the rarer species in iNat even if we can't identify them: but unfortunately it will not feed through to the HRS. There are 5 values that are relevant to UK (and European) species: Complete lateral scutum stripes, Partial lateral scutum stripes, "cleoae" pattern, interrupta-group, and cf. S scripta. 'Partial lateral scutum stripe' isn't very useful in the UK because the two species it includes are both identifiable to species (S. loewi and S rueppellii).

Distinguishing Sphaerophoria, and differences between the sexes.

Sphaerophoria are very elongate black and yellow hoverflies. They have a clear yellow stripe down the sides of at least the front half of the scutum. Males have a massive round genital capsule on the underside of the tip of their abdomen (hence the name 'Globetails'), which is diagnostic for the genus. Most males are very straight-sided, although some have the abdomen constricted near the front. Female abdomens have more convex sides, and the abdomen tip is rather pointed; also the frons usually has a fairly broad black stripe descending from the vertex (male frons is all yellow). Like most hoverflies (and all Syrphini), the eyes of males are connected, but the eyes of females are clearly separated (though the area between the eyes is black, which can sometimes make it hard to see).

Is the scutum stripe 'complete' or 'partial'?

One useful marker in identifying Sphaerophoria is whether the stripe at the side of the scutum stretches the full length of the scutum ('complete'), or whether it stops at the wing base ('partial'). Care needs to be taken with this because the stripe can be much fainter beyond the wing base - this still counts as 'complete'. When 'partial' it is truly shining black behind the the wing bases. A partial scutum stripe is a feature that separates both species in which both sexes are identifiable (S rueppellii and S loewi) from all the others.

Identifying S rueppellii from Photos

This is quite a distinctive species with an incomplete scutum stripe. The abdomen of both sexes is unusually bulbous - constricted near the front. The abdomen markings, especially in the female, are quite curved. Curved bars from the side of the abdomen meet or nearly meet in the middle, but on T2 the spots are usually well separated and blunt-tipped. The antennae are pale but may sometimes be darkened above - they are never truly black though. This species is widespread but only crops up on iNat occasionally.

Identifying S loewi from Photos

A very distinctive species - the only one with jet black antennae. The abdomen is very dark, with a unique pattern of oblique spots becoming less well separated toward the tip. The male abdomen tapers toward a constriction at the front. The female abdomen seems to be even more constricted, and T5-7 are clearly visible. The species is associated with reedbeds, especially those containing club-rushes, and most often coastal ones. It is extremely rare - there are two on iNat (females from Poland and France), the images of both sexes from Steven Falk are excellent

Identifying S scripta from Photos

Males are quite easily identifiable because the abdomen is remarkably long compared to the wings. When the wings are folded almost the whole of T5 is beyond the wing tips. In other species the wings almost entirely cover the abdomen. It is of course harder to judge this when the wings are open, and you have to be very careful to take into account the angle at which the photo is taken, and whether the abdomen is being held straight or bent down in order to judge whether the abdomen is long.

HRS will generally not accept a female S scripta ID from photos. But it is useful to add the 'cf S scripta' value in the 'Sphaerophoria Identifiable Group' observation field so that it is possible to separate out the many probable scriptas from the more unusual species. The females of S scripta are also a little longer than other species owing partly to a longer T5 - the effect is much more subtle. The images below show a female that is probably S scripta compared to one that is definitely not S scripta.

Only one feature is generally regarded as diagnostic for S. scripta females: there is a broad glabrous line on the underside of the hind femora (that is to say a smooth shiny line without black bristles). In other species this line is narrow, but in scripta it is almost as wide as the femur itself. This is extremely difficult to capture in a photograph. I have tried! The best way in the field is to get the fly in a spi-pot. Otherwise obviously a microscope does the trick!

So when should we make it Research Grade at genus?

When the lateral scutum stripe is complete AND EITHER
a) it is male with a short abdomen OR
b) it is female without an exceptional view of the underside of the hind femur showing the tiny black bristles and the glabrous strip between them.

The remaining sections are only relevant for using the 'Sphaerophoria identifiable group' observation field.
What is "cleoae" pattern?

The species "Sphaerophoria cleoae" was described by Metcalfe in 1917 from North American females, however it was later found to represent genetic abnormalities that can occur in the females of several species - including European species. (Some other elongate genera show analogous phenomena). Such females may lack ovaries/spermathecae - in terms of appearence the tergites and sternites toward the end of the abdomen are fused together into a ring shape, and therefore the abdomens are less pointy and more male-looking (so do check the head to determine male sex!). They are usually darker and the particular abdomen pattern is distinctive - with the bands broken (or weakened) in the lateral third.

interrupta-group

The rest of the species with a complete scutum stripe fall into two general categories - those with banded abdomens and those with spotted abdomens. Care must be taken however because dark individuals of banded species may look spotted and vice versa. The interrupta-group is for the usually distinctly spotted species, primarily interrupta and fatarum. (See examples - Some other species are sometimes described as 'usually spotted' but many images and diagrams contradict this - including Falk's - philanthus is the closest to being spotted, and often is so). In these two species the markings are usually very clearly separated, and the females have a very distinctive sort of pattern - I'm not sure about fatarum but interrupta also has a distinct black face stripe. Females are probably easier to determine because their spots are quite well formed with a distinctive shape. Using this will enable people to filter for spotted specimens (it doesn't matter enormously if we accidentally catch some dark normally-banded species.)

So how can we use the 'Sphaerophoria identifiable group' observation field?

The main value of this field is to separate the more unusual species from the things that are probably S scripta and make them searchable. This way they don't just get lost in 'Genus Sphaerophoria' RG observations. If S. loewi and rueppellii can be excluded then I suggest using 'cf S scripta' for the females that match the indications of scripta given above, using interrupta-group for those that seem clearly to be spotted species, and 'cleoae pattern' as described above; and then using 'Complete scutum stripe' as the fallback for things that don't fall clearly into those three.

Anything else to be aware of in Europe?

Since some of you do identifying in continental Europe too it is worth mentioning that there are two other species in the 'Partial lateral scutum stripe' group - and both are identifiable from photos, S shirchan is distinguished by the distinct black face stripe, and S estebani lives in the mountains of central Europe and is distinguished by not having the distinguishing features of the others! (i.e. antennae not jet black (cf loewi), not with a face stripe (cf shirchan), and not having a constricted abdomen (cf rueppellii) - according to van Veen it has elongate, straight, lemon-yellow bands of constant width which are sometimes interrupted in the middle, on shiny black tergites. There is also one species with no scutum stripe at all - Sphaerophoria nigra, which is endemic to the Azores - completely black apart from the bright yellow scutellum, and parts of the legs in females, so rather distinctive!