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
הועלה ב-אוקטובר 24, 2022 08:50 אחה"צ על ידי matthewvosper matthewvosper

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