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 | 18 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

December 31, 2021

Key to the Neotropical Eristalis

Here is a key to the Eristalis of the Neotropical region.

There is an excellent paper on 'The Eristalis Flower Flies of the Americas South of the United States' by F.C. Thompson. This covers all the species here, and includes a very useful key, as well as full descriptions of all the species. Almost all of my information comes from this paper. The Thompson key however includes some clauses not well tailored to photographic ID, and also includes a few Palpada species.

The advantages of doing another key are partly the opportunity to tailor it towards photographs, partly for accessibility, and partly as a consolidation of learning exercise for myself. The Neotropical Eristalis are mostly quite visually distinctive, and it is not necessary to resort to clauses such as 'aristae plumose or bare'.

I'm not quite covering the same area as the Thompson paper. The Mexican states bordering the USA can see species that are regarded as Nearctic: So Thompson includes E stipator, but E arbustorum is also recorded on iNat from those northern states, and there is the obvious potential for other species such as E hirta to cross the border. For that reason I'm not including the very North of Mexico: Species covered by this key are alleni, bellardii, bogotensis, circe, croceimaculata, gatesi, persa and tenax.

For the Nearctic Eristalis (including the northernmost states of Mexico) see the excellent key by @edanko and @zdanko.

The greatest difficulty in identifying Eristalis in this region is actually confusion with some of the many Palpada species. Bolder markings on the scutum, a bright scutellum, brighter markings generally, and thickened hind legs are all indications that you may in fact have a Palpada.

Posted on December 31, 2021 11:29 by matthewvosper matthewvosper | 9 comments | Leave a comment

December 24, 2021

Distinguishing Eristalis arbustorum and Eristalis abusiva

Eristalis abusiva is a rare Palearctic species of drone fly. It seems to increase in abundance towards the coast, but is found inland, and there are records from entirely landlocked countries. According to Barkalov (Checklist of the hover-flies (Diptera, Syrphidae) of Russia 2018) its range extends as far east as Japan.

As cool a species as it is, its main function in life seems to be to complicate the identification of the much more common E arbustorum, which is rather similar. Below I will give the standard means of distinguishing them and their pitfalls, but I will also try to supplement this with some thoughts of my own.

It is difficult to gauge the variability of a rare species. How many people have seen a large enough number? Here we see the value of a site like iNat, which might just have the biggest collection of abusiva specimens in the world! Male and female, and from a diversity of locations. (Still only 30 or so and counting). Some detailed pictures can also be found on Steven Falk's website

Thanks to @sbushes, @jeanpaulboerekamps, @waldgeist and @alexplayford for giving permission for me to use their pictures.

The characters covered are:
Published characters:
.1. Aristae
.2. Middle tibiae
.3. Male eyes
.4. Face stripe

Other Observations:
.5. Geography
.6. Face shape
.7. Hairiness
.8. Scutum dusting
.9. Female abdomen markings

Posted on December 24, 2021 11:17 by matthewvosper matthewvosper | 6 comments | Leave a comment

December 04, 2021

November 25, 2021

Identification of the major groups within Platycheirus (males)

The taxonomy of Platycheirus on iNat has recently had a bit of a sort out. The result is the use of the generic/subgeneric framework established by Mengual (2020), and within that the Species groups suggested by Vockeroth and developed by Young, Marshall and Skevington. These Groups are called 'Sections' in iNat, because that is the rank that is available. Within the albimanus Section are the complexes scutatus and clypeatus. So it looks like this:

Genus Pyrophaena (aka granditarsis Group) Holarctic
Genus Eocheilosia New Zealand
Genus Platycheirus Holarctic,Neotropical
Subgenus Tuberculanostoma (formerly a distinct Genus) Neotropical
Subgenus Pachysphyria (aka ambiguus Group) Holarctic
Subgenus Carposcalis (aka stegnus Group) New World
Subgenus Platycheirus Holarctic
Section manicatus Holarctic
Section peltatus Holarctic
Section chilosia Holarctic
Section pictipes Nearctic
Section albimanus Holarctic
Complex clypeatus Holarctic
Complex scutatus Holarctic
Not in a complex Holarctic

(European identifiers in particular should note that the definition of 'Section albimanus' used here still conflicts with the definition sometimes used in Europe i.e. those species with white maculae - as it did before. White spots species are spread through the groups. In the UK for example 4 species are considered albimanus Group in this 'white spots' sense: ambiguus is in Subgenus Pachysphyria, discimanus is in Section manicatus, but the other two (albiimanus + sticticus) are in Section albimanus. This is why the concept cannot be implemented in iNat - the taxa have different parents.)

The morphological delineation of the groups within the genus Platycheirus goes primarily with the modifications of the male foreleg. Here is an attempt at a key to the groups on that basis, largely based on Skevington:

1. a. At least some segments of the male foreleg modified in shape.
b. Male foreleg modified only by the presence of ornamental setae, if at all.
2
4
2. a. Male foretibia unmodified in shape (only tarsi expanded).
b. Male foretibia modified in shape.
Section manicatus
3
3. a. Male foretibia broadening gradually throughout its length.
b. Male foretibia broadened distinctly at the apex only.
Section albimanus
Section peltatus
4. a. Face extended well forwards into a prominent pointed snout, but hardly downwards, and with a prominent tubercle, Males dichoptic.
b. Face not extended forwards into a snout. Males holoptic.
Subgenus Tuberculanostoma
5
5. a. Male forefemur with long curled bristle at the apex.
b. Male forefemur without such a bristle.
Subgenus Pachysphyria
6
6. a. Long curled setae on male forebasitarsi.
b. Without long curled setae on male forebasitarsi.
Section chilosia
7
7. a. Male foretibia without ornamental setae (i.e. leg unmodified).
b. Male foretibia with long posterior setae.
Section pictipes
Subgenus Carposcalis
Posted on November 25, 2021 22:25 by matthewvosper matthewvosper | 0 comments | Leave a comment

October 31, 2021

Palloptera s.l.

This table forms part of a discussion on a flag (https://www.inaturalist.org/flags/542333#activity_comment_f72de246-215c-4f6b-be7a-7f3b2d0ca3d5), but was too large to post there: (Explanations of the justifications are in the flag)

Abbreviations:
Genera:
Palloptera=P, Toxonevra=X and Temnosira=M.
Sources:
SD - Systema Dipterorum
FE - Fauna Europaea
OZ - Ozerov, various papers
MZ - Merz https://www.e-periodica.ch/cntmng?pid=seg-001:1997:70::520
HYH - Han https://www.researchgate.net/publication/264147044_A_Checklist_of_the_Families_Lonchaeidae_Pallopteridae_Platystomatidae_and_Ulidiidae_Insecta_Diptera_Tephritoidea_in_Korea_with_Notes_on_12_Species_New_to_Korea/link/53d6230f0cf220632f3d872c/download
MC - Merz and Chen https://www.e-periodica.ch/cntmng?pid=seg-001%3A2005%3A78%3A%3A437
MS - Merz and Sueyoshi http://www.studia-dipt.de/con91.htm

Species iNat Proposed Genus For Against Justification
albertensis Johnson, 1921 N/A P Nearctic N/A Nearctic
alticola Ozerov, 1994 X X SD, OZ N/A Described by Ozerov - so could be Temnosira
ambusta Meigen, 1826 PM M FE, MZ SD (P), OZ (X) M not recognised by OZ
anderssoni Rotheray & MacGowan, 1999 P P SD, FE N/A Unanimity
basimaculata Czerny, 1934 N/A X OZ, FE, MZ SD (P) Discount SD when alone as (P)
bimaculata Strobl, 1910 P P SD, FE MZ (X) FE vs Merz - X not common
carterosoma Ozerov, 1993 X X SD,HYH, OZ N/A Described by Ozerov - so could be Temnosira - but HYH did not reassign
claripennis Malloch, 1924 P P Nearctic N/A Nearctic
czurkini Ozerov, 1993 N/A M SD OZ (X) M not recognised by OZ - one of two he says are difficult to place
elegans Merz & Chen, 2005 N/A P SD, MC N/A Unanimity
ephippium Zetterstedt, 1860 X X OZ, FE, MZ SD (P) Discount SD when alone as (P)
flava Oldenberg, 1910 N/A P SD, FE, MZ N/A Unanimity
formosa Frey, 1930 P P SD, OZ, FE, MZ N/A Unanimity
gavryushini Ozerov, 2019 N/A X OZ N/A Described by Ozerov - so could be Temnosira
jucunda Loew, 1863 N/A X Nearctic N/A Nearctic
kloiberi Morge, 1967 N/A X MZ SD (P) Discount SD when alone as (P)
kukumorensis Czerny, 1934 N/A P SD, MC N/A Unanimity
laetabilis Loew, 1873 X X OZ, FE, MZ SD (P) Discount SD when alone as (P)
longipennis Czerny, 1934 P X OZ SD (P) Discount SD when alone as (P) - Ozerov only - but he does not mention it as a difficult placement
maculifemur Czerny, 1934 N/A P SD, FE MZ (X) FE vs Merz - X not common
marginata Meigen, 1826 P P SD, OZ, FE, MZ N/A Unanimity
modesta Meigen, 1830 PX X OZ, FE, MZ SD (P) Discount SD when alone as (P)
muliebris Harris, 1780 X X SD, OZ, FE, MZ N/A Unanimity
nigriscutata Ozerov, 1993 N/A M SD OZ (X) M not recognised by OZ - one of two he says are difficult to place
orientata Kovalev, 1972 N/A X OZ, HYH SD (P) Discount SD when alone as (P)
pallens Loew, 1873 N/A X FE, MZ SD (P) Discount SD when alone as (P)
paralia Ozerov, 1993 N/A X SD, OZ N/A Described by Ozerov - so could be Temnosira
quinquemaculata Macquart, 1835 PX X OZ, FE, MZ SD (P) Discount SD when alone as (P)
saltuum Linnaeus, 1758 PM M FE, MZ SD (P), OZ (X) M not recognised by OZ
scutellata Macquart, 1835 P P SD, FE, MZ N/A Unanimity
septentrionalis Czerny, 1934 N/A X MZ SD (P) Discount SD when alone as (P)
setosa Melander, 1913 N/A P Nearctic N/A Nearctic
shakhadarana Ozerov, 2010 N/A X SD, OZ N/A Described by Ozerov - so could be Temnosira
shatalkini Ozerov, 1993 N/A M SD OZ (X) M not recognised by OZ
similis Johnson, 1910 N/A X Nearctic N/A Nearctic
simillima Merz & Sueyoshi, 2002 N/A M SD, MS N/A Unanimity
striata Merz & Sueyoshi, 2002 N/A X SD, MS N/A Unanimity
subarcuata Johnson, 1921 M M Nearctic N/A Nearctic
subusta Malloch, 1924 P P Nearctic N/A Nearctic
superba Loew, 1861 N/A X Nearctic N/A Nearctic
terminalis Loew, 1863 N/A P Nearctic N/A Nearctic
trichaeta Ozerov, 1993 N/A M SD OZ (X) M not recognised by OZ
trimacula Meigen, 1826 PX X OZ, FE, MZ SD (P) Discount SD when alone as (P)
umbellatarum Fabricius, 1775 P P SD, OZ, FE, MZ N/A Unanimity
usta Meigen, 1826 P X OZ, FE, MZ SD (P) Discount SD when alone as (P)
ustulata Fallén, 1820 P P SD, OZ, FE, HYH, MZ N/A Unanimity
venusta Loew, 1858 N/A X OZ, FE, MZ SD (P) Discount SD when alone as (P)
Posted on October 31, 2021 21:00 by matthewvosper matthewvosper | 0 comments | Leave a comment

October 27, 2021

Thoughts on the iNat taxonomy of Platycheirus

This post forms part of a discussion on a flag (https://www.inaturalist.org/flags/496291#activity_comment_9906ca40-8da7-489f-bcda-e6c0516f5b16) - but I couldn't embed the spreadsheet there

This covers just over 130 species - there are said to be around 220 in total. It should include all of the Nearctic (North of Mexico) and all of Europe except muelleri and laskai.

SOURCES:
General:
Mengual https://brill.com/view/journals/ctoz/89/2/article-p210_210.xml#R000026%20R000088%20R000111

Young/Marshall/Skevington https://www.mapress.com/zt/article/view/zootaxa.4082.1.1/4574

SOURCES:
General:
Mengual https://brill.com/view/journals/ctoz/89/2/article-p210_210.xml#R000026%20R000088%20R000111
Young/Marshall/Skevington https://www.mapress.com/zt/article/view/zootaxa.4082.1.1/4574

For peltatus group
van Steenis – (considered as a subgroup of albimanus group = Subgenus Platycheirus)
https://www.researchgate.net/publication/269107486_Description_of_and_key_to_the_European_females_of_the_Platycheirus_peltatus_sub-group_Diptera_Syrphidae_with_description_of_the_male_and_female_of_P_islandicus_Ringdahl_1930_statn
Limited to Europe

For scutatus group
Doczkal - https://www.zobodat.at/pdf/Volucella_6_0023-0040.pdf
Limited to Europe
plus YMS for atlasi (North African)

For clypeatus group
Ball and Morris British Field Guide (see comments in post)
and Haarto
https://www.researchgate.net/publication/281206992_The_description_of_the_female_of_Platycheirus_troll_Mutin_Diptera_Syrphidae_with_a_preliminary_key_to_the_Northern_Palaearctic_females_of_the_Platycheirus_clypeatus_group
Covers Whole Palearctic - according to title implication but I don’t have access
And
van Veen field guide for angustipes
and
Dipterists digest No 5 1990 Speight

For ambiguous group
Barkalov - as ‘Subgenus Pachysphyria’ http://kmkjournals.com/upload/PDF/EEJ/17/eej17_6_466-510_Barkalov.pdf covers whole of Russia
and Nielsen - as 'ambiguus group' https://www.zobodat.at/pdf/Volucella_7_0001-0030.pdf covers Europe

for manicatus group
Nielsen and Barkalov - https://www.researchgate.net/publication/319312480_A_revision_of_and_key_to_the_Holarctic_and_Oriental_Platycheirus_manicatus_group_species_Diptera_Syrphidae
Covers Holarctic and Oriental species
Plus YMS for sticticus (see tree p98) EDIT: although YMS resolve it with other species in manicatus, it has an expanded male fortibia, and is not listed as manicatus group by Nielsen and Barkalov above - so it is placed in albimanus group.

For a couple of oriental and Asian species see also
http://www.entomologi.no/journals/nje/2016-2/pdf/nje-vol63-no2-169-174-nielsen.pdf for albotibeticus and formosanus
https://www.researchgate.net/publication/330319469_The_species_of_the_genus_Platycheirus_Lepeletier_Serville_1828_Diptera_Syrphidae_from_Taiwan_with_a_discussion_on_intersex_specimens for perpes
https://www.researchgate.net/publication/316505699_New_material_of_Central_Palaearctic_Platycheirus_Diptera_Syrphidae_with_description_of_three_new_species for dudkoi, latens and transbaikalicus

Posted on October 27, 2021 23:23 by matthewvosper matthewvosper | 6 comments | Leave a comment

October 14, 2021

Eristalis: Distinguishing males of E rupium and E jugorum

Some time ago I was working on a key to European Eristalis (still working on it every now and then!). It seems a good way of learning new criteria for distinguishing the species, and the keys I know, excellent as they are, are not primed for identifying from photographs (the first couplet is often 'aristae plumose or bare'!) - maybe it will get posted here at some point!

Anyway, I was aware of the black posterior fringe of hairs on the front femora of E jugorum males (a handy way to distinguish from horticola males from the key of van Veen. And while working on the difficult 'yellow-hind-metatarsus group' I became aware that E rupium and E obcura males also have a posterior fringe of black hairs on the front femur. It suddenly dawned on me that a male rupium with a dark hind metatarsus could be very hard to distinguish from a male jugorum if there wasn't a good angle on the face.

Soon after, flo-dycob queried an observation I had identified as a male jugorum, and I knew I'd run into precisely this problem.

Well it's taken a while, but here are some features I think can be used to distinguish male rupium and jugorum. Individually some may be more or less reliable, but I think it's a good package. Comments and corrections most welcome!

jugorum rupium
Face produced forwards and down Face produced down only.
Hind metatarsus black, never yellow, swollen Hind metatarsus black to yellow, not swollen.
Femur 1 with dense posterior fringe of black hairs Femur 1 with sparse posterior fringe of black hairs
Femur 2 with posterior fringe of pale hairs Femur 2 with posterior fringe of black hairs at least apically
Stigma short Stigma elongate
T2 spots occupy almost whole lateral margin when fully formed, inner angle just subrectangular T2 spots end well before the hind margin laterally even when fully formed, inner angle distinctly acute.
T3 pale haired T3 posteriorly extensively black haired.
Frons pale haired (dark ground colour shows through) Frons with black hair.
Subcosta yellowish at base Subcosta brown at base
Scutellum distinctly brighter than scutum Scutellum and scutum not contrasting in colour

I would just add that to me the general appearance of these flies is that male jugorum are rather bright, bushy and tidy flies, whereas male rupium often (but not always) seem rather dull and scrawny.

Posted on October 14, 2021 22:18 by matthewvosper matthewvosper | 0 comments | Leave a comment