October 24, 2022

Key to British Female Platycheirus Incorporating the Main Infrageneric Groupings in iNat

It is best to interpret these keys with sight of quality pictures such as the excellent resource by Steve Falk

In constructing this I have used information from the helpful Book 'Britain's Hoverflies' by Ball and Morris, the key in 'Hoverflies of Northwest Europe' by M.P. van Veen and Steve Falk above.

Some of these species are genuinely impossible to ID from a photo, but I hope that this key might enable more of them to reach a finer level of ID. The female of P. aurolateralis is unknown

For an overview of how the taxonomic groupings used by the UK Hoverfly Recording Scheme relate to the taxa available on iNat see here. For the key to males see here.

Note that the distinctive rosarum and granditarsus have departed for Genus Pyrophaena.

This key is intended to be as useful as possible when IDing from photos, but this will frequently be impossible. Used with a little circumspection I hope it is at least helpful. Be especially aware that it is often difficult in photographs to tell the difference between grey and pale yellow spots. I am very happy to be informed of any errors.

Females:

1. a. Abdomen with broad, but often obscure, grey bands on T3-4 and similarly broad grey spots on T2; the frons is mostly black - a narrow line of dusting extends up the eye margin and ends in small inward pointing triangles above the lunule which may or may not be connected by a narrow line of dusting across the top of the lunule.
b. Abdomen spotted
Subgenus Pachysphyria




Subgenus Platycheirus
P. ambiguus




2
2. a. All femora mostly black; either orange spotted species with face produced forward into a snout or grey spotted species with frons undusted; normally with markings on T5.
b. Face not produced forward into a snout; extensive yellow parts on at least some femora; if grey spotted then femora 1 and 2 almost entirely yellow; with or without markings on T5.
Section manicatus


Subgenus Platycheirus cont…
6


3
3. a. Grey spots; femora 1 and 2 almost entirely yellow (but beware they may darken somewhat in the middle); the frons black with at most small dust markings laterally.
b. Orange spots; femora 1 and 2 with or without black parts; frons more significantly dusted.
Section albimanus (no complex)


Subgenus Platycheirus cont…
10


4
4. a. Small rectangular spots on T3-4, wider than long, smallest on T2. No spots on T5 (or occasionally very obscure); antennal flagellum partly yellowish (can be hard to see from above).
b. Larger, less elongate spots. Clear spots on T5 (Except in P. angustatus which usually also lacks spots on T4 (and P. amplus?) and perhaps melanic specimens but then other spots not as described above).
Section albimanus, Complex scutatus


Subgenus Platycheirus cont…
End


5
5. a. Antennal flagellum completely black; Spots on T2 roundish, positioned closer to the hind edge of the tergite and smaller than on T3-4
b. Antennal flagellum partly yellowish (can be hard to see from above); Spots on T2 usually larger than on other tergites, positioned closer to the front of the tergite and with hind margin distinctly angled backwards toward the midline - otherwise T2 spots greatly reduced, nearer to the hind edge and kidney shaped, (P. amplus) [If the spots on T2 are the largest but the hind margin is flat reconsider whether it could be Section manicatus]
Section albimanus, Complex clypeatus

Section peltatus
11

9
SECTION MANICATUS
6. a. Greyish Spots; face not produced forward into a blunt snout; frons undusted and particularly wide.
b. Orange-yellow spots, face produced forward into a blunt snout.


Section manicatus cont…
P discimanus

7
7. a. Face and frons shining black, only slightly dusted on the eye margin; mouth edge not quite projecting beyond the tubercle; scutum shining black.
b. Face and frons significantly grey dusted; mouth edge protruding past the tubercle or not.


Section manicatus cont…
P melanopsis

8
8. a. Mouth edge projecting beyond the tubercle; scutum grey dusted; frons wholly dusted, even around the vertex.
b. Scutum shining black; mouth edge not quite protruding past the tubercle; frons extensively dusted, but not on the vertex, and not so much medially.


P manicatus

P. tarsalis
SECTION PELTATUS
9. a. Spots on T2 larger than on T3-4, with hind margin sloping distinctly backwards toward the midline, reaching close to the anterior margin of the tergite.
b. Spots on T2 smaller than on T3, at least greatly reduced, kidney shaped, and far from the anterior margin of the tergite.
Section peltatus



End


P. amplus
SECTION ALBIMANUS (No complex)
10. a. Frons with narrow, but normally very clear, dusting on the eye margin ending in a small spot; S2 with long hairs; posterior anepisternum wholly dusted.
b. Frons undusted or only indistinctly on the eye margin; S2 with only short hairs; lower part of posterior anepisternum shining.
P. albimanus

P. sticticus
COMPLEX CLYPEATUS
11 a. Hind femur completely yellow; T6 with yellow markings.
b. Hind femur with at least a black ring; T6 with or without yellow markings.
Complex clypeatus cont...
Complex clypeatus cont...
12
13
12 a. Frons shining black between and below the lateral dust spots
b. Frons vaguely dusted between and below the lateral dust spots.

P. fulviventris
P. perpallidus
13 a. Hind leg wholly black except at the knee. T6 black.
b. Hind leg with more yellow (at least also the apex of the tibia); T6 with or without yellow markings.

Complex clypeatus cont...
P. podagratus
14
14 a. T6 with yellow markings.
b. T6 without yellow markings.
Complex clypeatus cont...
Complex clypeatus cont...
15
16
15 a. T2 spots large; forefemur without a subbasal white bristle; posterior anepisternum shining on the lower half, dusted on the upper half.
b. T2 spots distinctly smaller; forefemur with a subbasal white bristle; posterior anepisternum wholly dusted.

P. scambus

P. immarginatus
16 a. Sides of thorax strongly shining; without spots on T5 and usually also T4.
b. Sides of thorax more dusted; T4-5 with spots.

Complex clypeatus cont...
P. angustatus
17
17 a. Frons with small widely separated lateral spots, the frons black between.
b. Frons with larger dust spots, often with some more obscure dusting between.

Complex clypeatus cont...
P. europaeus
18
18 a. Spots on T3+4 narrowly separated from the front margins of the tergites and not larger than half the length of the tergites.
b. Spots on T3+4 meeting the front margins of the tergites and distinctly larger than half the length of the tergites.


Complex clypeatus cont...
P. occultus

19
19 a. Posterior hair fringe on forefemur confined to the basal half.
b. Posterior hair fringe on forefemur extending to the apex.

P. ramsarensis
P. clypeatus
Posted on October 24, 2022 20:50 by matthewvosper matthewvosper | 0 comments | Leave a comment

October 20, 2022

Key to British Male Platycheirus Incorporating the Main Infrageneric Groupings in iNat

It is best to interpret these keys with sight of quality pictures such as the excellent resource by Steve Falk

In constructing this I have used information from the helpful Book 'Britain's Hoverflies' by Ball and Morris, the key in 'Hoverflies of Northwest Europe' by M.P. van Veen and Steve Falk above.

Some of these species are next to impossible to ID from a photo, but I hope that this key might enable more of them to reach a finer level of ID.

For an overview of how the taxonomic groupings used by the UK Hoverfly Recording Scheme relate to the taxa available on iNat see here

Note that the distinctive rosarum and granditarsus have departed for Genus Pyrophaena.

This key is intended to be as useful as possible when IDing from photos, but this will frequently be impossible. Used with a little circumspection I hope it is at least helpful. I am very happy to be informed of any errors.

Males:

1. a. Abdomen with paired grey maculae; face and frons entirely grey dusted; frons is quite large when viewed from above; Foreleg unmodified in shape; femur with apical curled bristle.
b. At least some foreleg segments modified in shape; no curled bristle at the apex of the fore femur; if grey spotted then with at least some shining black undusted parts on frons.
Subgenus Pachysphyria

Subgenus Platycheirus
P. ambiguus

2
2. a. Foretibia not broadened towards the apex; at least foretarsi 1+2 enlarged to produce a smooth curved shape; if abdominal spots are orange then face produced beneath the tubercle into a blunt snout.
b. Foretibia broadened toward the apex; forebasitarsus enlarged in a smooth rounded shape or with pointed corners; face flattish beneath the tubercle.
Section manicatus


Subgenus Platycheirus cont…
4


3
3. a. Orange spots. Foretibia sharply broadened only at the apex; forebasitarsi greatly enlarged, significantly overhanging the tarsi on the inside and with an acute corner on the inside apex; posterior surface of forefemur covered with strong flattened black hairs; middle femur with deep anterior concavity; fore and middle femora never all yellow.
b. Orange or grey spots; Male foretibia broadening throughout most of its length; forbasitarsi expanded into a smooth curved shape; forefemur without flattened black hairs; middle femur without concavity; fore and middle femora may be yellow or not.
Section peltatus



Section albimanus
7



9
SECTION MANICATUS
4. a. Greyish Spots, face not produced forward into a blunt snout.
b. Orange-yellow spots, face produced forward into a blunt snout.

Section manicatus cont…
P discimanus
5
5. a. Face and frons shining black, mouth edge not quite projecting beyond the tubercle; foretarsi 1-3 expanded, pale and tapering towards 4-5 (black); scutum shining black.
b. Face and frons grey dusted; if scutum shining black then only foretarsi 1+2 expanded; mouth edge protruding past the tubercle or not.


Section manicatus cont…
P melanopsis

6
6. a. Mouth edge projecting a little beyond the tubercle; foretarsi 1-3 expanded, pale and tapering towards 4-5 (black); scutum grey dusted; broader bodied; abdominal spots reaching close to the hind margin of the tergites.
b. Scutum shining black; foretarsi 1+2 expanded; mouth edge not quite protruding past the tubercle; narrower bodied; spots not reaching close to the hind margins of the tergites.



P manicatus


P. tarsalis
SECTION PELTATUS
7. a. Larger species; spots on T2 well formed (but not large); middle tibia with moderate ventral swellings at 1/3 length and apex, the former with an indistinct tuft of moderate length black hairs.
b. Smaller species; spots on T2 poorly formed or absent; middle tibia with ventral swellings absent or strong and a distinct flag of long black hairs at 1/3-1/2 length.



Section peltatus cont…
P peltatus


8
8. a. Middle tibia with hardly any ventral swellings at 1/3 length or apex, but with an anterior hair tuft.
b. Middle tibia with pronounced ventral swellings at mid length and apex but no anterior hair tuft; a tuft of hairs arising from the apical swelling pointing upwards parallel to the tibia.
P amplus

P nielseni
SECTION ALBIMANUS
9. a. Normally greyish spots; spots never nearly filling the length of the tergites; if poorly formed and even absent on T2 then the foretibia widening gradually throughout its length, and not greatly expanded; forefemur with only one long posterior black bristle in the apical half (much longer than the surrounding bristles).
b. Normally orange-yellow spots; spots usually well formed, in many species more than 1/2 the length of the tergites; if spots very poorly formed and even absent on T2 then the forefemur expanded suddenly more towards the apex than the rest of the length and with a distinct tuft of black hairs prior to the apical expansion; forefemur may have more long black posterior bristles or not.
Section albimanus cont…



Section albimanus cont…
10



11
10. a. Spots normally fairly well formed except sometimes on T2 with hind margin sloping forwards medially; foretibia greatly broadened; Forefemur without a long wirey posterior bristle at the apex, but with two basal L-shaped tufts of tangled bristles.
b. Spots poorly formed, even missing on T2; foretibia only slightly broadened; Forefemur with a long wirey posterior bristle at the apex, but without basal L-shaped tufts.
P albimanus


P sticticus
11 a. Large orange spots (>1/2 length of tergites 3+4). Without two hooked tufts of bristles at the base of forefemur; metacoxae normal.
b. Small squarish orange spots; Two hooked tufts of bristles at the base of forefemur; metacoxae with finger-like process.
Complex clypeatus

Complex scutatus
13

12
COMPLEX SCUTATUS
12. a. Face and frons wholly silver dusted; spots on T2 well formed.
b. Frons dark or obscurely golden dusted; very obscure abdominal spots especially on T2 where they are usually missing entierly; middle tibia particularly hairy.
c. Frons black; abdominal markings well formed.
P. scutatus
P. aurolateralis

P. splendidus
COMPLEX CLYPEATUS
13 a. T2 with large spots (>1/2 length of tergite).
b. T2 with small spots (<1/2 length of tergite).
Complex clypeatus cont...
Complex clypeatus cont...
14
18
14 a. Hind leg black except narrowly yellow at the knee. T5 black. Foretibia exanded suddenly in the apical 1/3, rounded, curving in again toward the apex.
b. Hind femur, tibia and usually tarsi with some yellow. T5 with yellow markings. Foretibia expanded differently and not curving back in again.


Complex clypeatus cont...
P. podagratus

15
15 a. Hind femur and tibia yellow. Foretibia expanded suddenly in about the apical half, remaining parallel sided to the apex.
b. Hind femur and tibia with some black. Foretibia expanding more gradually from the base to the apex.


Complex clypeatus cont...
P. fulviventris

16
16 a. Forefemur without a basal tuft of long white hairs, but with a posterior row of long strong black bristles. Foretibia, although it expands from the base it contracts again at about 2/3 length before expanding again to the end; black hind border of tergites not much narrower than the width of the black midline.
b. Forefemur with a basal tuft of long white hairs, with or without a posterior row of long strong black bristles; Foretibia expanding continuously from base to apex; black hind border of tergites very narrow or absent - much narrower than the width of the black midline.




Complex clypeatus cont...
P. scambus



17
17 a. Forefemur with a posterior row of long black strong bristles.
b. Forefemur without a posterior row of long black strong bristles, instead with dense, mainly yellow, hair. Apex of middle femur with anteroventral black hairs bent backwards.

P. immarginatus
P. perpallidus
18 a. Notably slender species; pleura distinctly shining, undusted; Forefemur with long black hairs in the basal half sharply bent at their tips. Underside of forebasitarsus with a v-shaped incision. In direct comparison with P. europaeus, the spots on T3 longer.
b. Broader species, though *P. europaeus* is also quite slender; pleura at least partly dusted. Forefemur without such hairs. Underside of forebasitarsus with or without a v-shaped incision.



Complex clypeatus cont...
P. angustatus


19
19 a. Underside of forebasitarsus with a v-shaped incision. Fairly slender species. In direct comparison with P. angustatus, the spots on T3 shorter.
b. Broader species; Underside of forebasitarsus without a v-shaped incision.


Complex clypeatus cont...
P. europaeus

20
20 a. Underside of forebasitarsus with a short narrow pale bare area stretching from the base to a darkened pit in the basal half.
b. Underside of forebasitarsus with a longer narrow pale bare area stretching from the base to a darkened pit in the apical half. Distinctly broader species.


Complex clypeatus cont...
P. occultus

21
21 a. Forefemur with a posterior hair fringe reaching the apex.
b. Forefemur with a posterior hair fringe confined to the basal half.
P. clypeatus
P. ramsarensis
Posted on October 20, 2022 20:17 by matthewvosper matthewvosper | 0 comments | Leave a comment

October 17, 2022

Mapping UK Platycheirus recording groups onto iNat taxonomy

The Genus Platycheirus is a very large, nearly cosmopolitan genus of small elongate hoverflies typified by males with distinctive modifications to the shape and/or bristles of parts of the front leg. The fact that it is such a large genus means that it has been subdivided. Traditionally the subdivisions have been based on the morphology of these male forelegs.

In the UK, for the purposes of the National Hoverfly Recording Scheme, the genus has been split up into 'groups'. This is not a taxonomic statement, but one of convenience for recording by grouping similar looking species together. Of course it is often the case that 'looking similar' does have taxonomic significance, and most of the UK groups do indeed align with more widely used taxonomic units. The exception, as we shall see, is the albimanus-group.

The UK groups are:
albimanus-group: inc. albimanus, ambiguus, discimanus, sticticus
manicatus-group: inc. manicatus, tarsalis, melanopsis
peltatus-group: inc. peltatus, nielseni, amplus
scutatus-group: inc. scutatus, aurolateralis, splendidus
clypeatus-group: inc. clypeatus, angustatus, europaeus, fulviventris, immarginatus, occultus, perpallidus, podagratus, ramsarensis, scambus
(Note that Subgenus Pyrophaena i.e P. granditarsus + rosarum is considered a full genus in iNat, not part of Platycheirus at all)

Apart from the UK albimanus-group, all of the above mentioned groups have equivalents in iNat such that if you have a species identified as one of those UK groups it is fine to ID them as 'Section P peltatus', 'Section P manicatus', 'Complex P. clypeatus', or 'Complex P. scutatus' respectively.

The UK albimanus group however, which depends on the whitish or bronzish abdominal markings (as opposed to yellow in other species) could not be reconciled with a wider taxonomy from the literature. It is handy for recording convenience in the UK - but breaks down quickly under the weight of overseas species, and is not taxonomically meaningful anyway. 'Section P. albimanus' in iNat is a completely different concept. In fact 'Section P. albimanus' in iNat includes 'Complexes clypeatus and scutatus' (Which is why we had to use Sections and Complexes to implement these groups). In addition, two species of the UK albimanus group are not in 'Section P. albimanus' (P ambiguus and discimanus). Here is how it looks:

Genus Platycheirus
---Subgenus Pachysphyria (inc. ambiguus - this whole Subgenus is characterised by a curled apical bristle on the male forefemur)
---Subgenus Platycheirus (inc. everything except ambiguus)
------Section P peltatus (same as the UK group)
------Section P manicatus (=UK group + discimanus)
------Section P albimanus (=albimanus, sticticus and the two complexes mentioned below)
---------Complex P scutatus (same as UK group)
---------Complex P clypeatus (same as UK group)

Another way to look at this is:
If you know the UK group
you can give it the same ID on iNat unless there is a possibility that it is ambiguus or discimanus.
If you have an ID from iNat, the UK group will be the same unless the ID is albimanus-group and the spots are not grey, or the ID is manicatus-group and the spots are grey (but the latter case is unlikely to occur in practice).

I hope that makes some sense. I have intended to put out a key to help with this, but it will have to wait. Maybe not long...

Posted on October 17, 2022 20:35 by matthewvosper matthewvosper | 0 comments | Leave a comment

July 16, 2022

Key to the Eriozona, Leucozona and Flavizona of the World

Well this has turned out to be a challenging group!

Here we have a cluster of genera that contain the Syrphine bumblebee mimics, and a bunch of things with white markings. They're cool, and not so common. In fact many of them are very obscure. A lot of this key is based on verbal descriptions alone - and sometimes not very detailed ones at that - so it needs to be treated with considerable care.

Species included:
Eriozona:
analis, nigroscutellata, syrphoides, tricolorata

Leucozona (Leucozona)
americana, brunetti, flavimarginata, inopinata, kingdonwardi, lucorum, nigripila, pruinosa, virendra

Leucozona (Ischyrosyrphus)
beybienkoi, glaucia, laternaria, sivae, transifasciatus, ussuriensis, velutina, xylotina

Flavizona
dolichostigma

Posted on July 16, 2022 23:03 by matthewvosper matthewvosper | 8 comments | Leave a comment

June 27, 2022

Distribution of Colour Forms in Volucella bombylans

In iNaturalist we are able to identify the named colour forms of Volucella bombylans.

I have tried to add these to as many V bomblylans observations as possible to see if anything interesting emerges. Because a great many of these observations are not yet Research Grade at the level of 'form' the data below are taken for searches including any ID of that form using the "ident_taxon_id =" URL.

The forms are:
f. bombylans - all black haired but for a red haired tail.
f. plumata - yellow haired around the sides and back of the scutum, and the base of the abdomen, with a white tail.
f. haemorrhoidalis - as plumata but with a red tail.
There are other rare forms that are unnamed.

Conventional wisdom is that f. plumata is the most common form with about 2/3 prevalence, f. bombylans constitutes almost all the rest. This is borne out in iNat data: of 1387 observations 883 are f. plumata (64%), 451 f. bombylans (33%) and just 53 f. haemorrhoidalis (4%).

However they do not appear to be evenly distributed. I haven't looked for any research on this, so it's perhaps likely things are already known, but I thought I'd put them out there anyway.

f. plumata



.
.
.
f. bombylans



.
.
.
f. haemorrhoidalis


According to the iNat data, it would seem that f bombylans is quite restricted to the area between the Pyrenees (or really central France) and the Urals.

There are no f. bombylans observations in Asia, compared to 21 f. plumata and 1 f. haemorroidalis (one would have expected about 7).

There is only one f. bomblyans observation southwest of a diagonal line across France from St Malo to St Tropez - that is on the West coast of France. None at all in Iberia - again one would have expected about 6 or 7 from 19 Iberian observations.

The other interesting thing about Iberia is the overrepresentation of f haemorrhoidalis. The Iberian observations break down as 12 f. plumata and 7 f. haemorrhoidalis, that is very similar to the 2:1 ratio normally observed between f. plumata and f. bomblyans, as if f. haemorrhoidalis somehow replaces f. bombylans in Iberia.

There are also no f. bombylans in Scotland, out of 25 observations.

The numbers are fairly small and I've done no statistical analysis of the significance of this, but it certainly seems quite interesting.

Posted on June 27, 2022 13:58 by matthewvosper matthewvosper | 7 comments | Leave a comment

June 13, 2022

Key to the Didea, Dideomima, Asiodidea and Megasyrphus of the World

These are the Syrphine genera with a dipped radial vein.

This has been a bit of a challenge, but quite a lot of fun. Use this key with caution of course, some of these species are very poorly known, others very variable. The genus Didea in particular I think needs revision, and who knows if geographic variation is hiding distinct species currently under the same name?

Anyway, I hope at least this disseminates some information about these rather nice species.

Posted on June 13, 2022 22:54 by matthewvosper matthewvosper | 3 comments | Leave a comment

May 31, 2022

Key to the Doros of the World

Doros!

I've not had much capacity the last few months, far too many curveballs to deal with. But I think this was a lunch-break well spent.

Posted on May 31, 2022 23:18 by matthewvosper matthewvosper | 2 comments | Leave a comment

February 04, 2022

Key to the Syrphus of North America

Here is an attempt at a key to the Genus Syrphus in North America. It is not always possible to identify to species from photos in this genus: many keys (including Vockeroth 1983, and van Veen (Europe)) start with features like the distribution of microtrichia on the wing membrane, and make heavy use of the colour of bristles on the knees or spicules under the middle basitarsus - so they are not exactly primed for photo ID! Hopefully the arrangement of this key makes the genus a little more accessible to photo ID, and crucially exposes some information on those rare species that create nagging doubts in the back of the mind. Many observations will still not be identifiable to species however.

One of the difficulties of identifying in this Genus is being sure of the genus in the first place! There are included some pointers to help with that. I have also included a slide of information on European Syrphus because there is significant overlap.

I have not illustrated the key itself (although there are images on some of the introductory slides), however the names of species at the points they key out are hyperlinked to iNat observations. Bear in mind that for many species, there are no iNat observations however: it is my hope that this key might help to dig them out! Many species are sexually dimorphic, so when comparing images, be sure to compare with the correct sex.

Please let me know of any errors of fact or clarity.

The species covered are:
attenuatus, currani, intricatus, knabi, opinator, rectus, ribesii, sexmaculatus, sonorensis, torvus, and vitripennis. There are also some comments on dimidiatus Fabricus 1781, dimidiatus Macquart 1834, doesburgi and monoculus.

Posted on February 04, 2022 00:12 by matthewvosper matthewvosper | 19 comments | Leave a comment

January 16, 2022

Key to the Syrphus of Europe

Syrphus is the type Genus of the Hoverflies. It is literally typical. But identification in this genus from photographs is hard, and often impossible. Information on the rarer species is also difficult to find. Here is my best effort at a key to this group that is optimised for photographs. Comments and corrections are especially welcome given that it's such a tricky group.

The species covered are admirandus, attenuatus, auberti, nitidifrons, ribesii, sexmaculatus, stackelbergi, torvus and vitripennis.

Posted on January 16, 2022 14:45 by matthewvosper matthewvosper | 0 comments | Leave a comment

January 06, 2022

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