Submission of a record is the start of a chain of processes that are used to ‘verify’ the data submitted. In essence, we ask some basic questions.
Where photographs are submitted, they are evaluated by somebody with suitable experience. Photographs posted to the Facebook group are evaluated by a number of more experienced members (a refined form of crowd-sourcing) and ultimately by Roger Morris or one of several European specialists where appropriate.
We have found that there is a high degree of misidentification by some recorders and therefore we have to treat datasets that are not supported by photographs or specimens with a lot of caution. Records submitted without a photograph therefore undergo additional scrutiny. For example, do we actually know anything about the ability of the recorder? Does the recorder take specimens or do they rely on field observations/photographs? What is the composition of the dataset: i.e. does it almost entirely consist of a small suite of common and easily identified species? In short, we try to assess the recorder's level of expertise and use this to guide the level of scrutiny needed.
Using the iRecord platform we may mark records as "plausible", which means that they exist on that platform but are not absorbed into the HRS dataset; occasionally they may be rejected because they cannot be verified. Records submitted in other ways will get marked as "unconfirmed" in the HRS dataset if there is doubt. If a recorder retains specimens, we may ask to see them to ensure accuracy.
Please note that there are some species complexes where males can be identified but females are more problematic or cannot be identified without DNA analysis. There is also one complex that can only be reliably identified from larvae or puparia (Microdon mutabilis/myrmicae).
The following are the most challenging:
Cheilosia albitarsis/ranunculi – males can only be separated on microscopic characters that are rarely visible in field photographs. Females cannot be separated except using DNA. Field photographs and females should therefore be logged as Cheilosia albitarsis sl. (sl. is shorthand for sensu lato – in the broad sense – which refers to the species from which the other species was split in recent years (back to 1990 for most species in modern lists but far further back for old diary records). We may want to check records based on specimens, especially of C. ranunculi from Scotland/northern England.
Dasysyrphus venustus/neovenustus/hilaris – a recent split that uses characters that are not wholly stable. The most useful character seems to be on sternite 2 combined with facial colour but reviews of museum specimens highlight intermediates that cannot be reliably assigned. Records based on retained specimens will be accepted, as will those in which the critical facial and sternite characters have been photographed, but all others are assigned to D. venustus sl.
Eumerus narcissi/sogdianus/strigatus - can only be separated reliably using characters of the male terminalia. Unfortunately, females of these species are not separable. These complications mean that these species are logged as "Eumerus sp." unless they are males supported by a specimen. In addition, E. funeralis is split on the basis of hair patterns on the underside of the hind femur, a feature that is extremely had to see and is rarely visible in photographs; consequently, this species is also logged as "Eumerus sp." unless supported by a specimen.
Platycheirus clypeatus/europaeus/occultus/ramsarensis – males can be separated on a combination of features involving pits on the underside of the front tarsi and hairs/patterns on the legs. Females, whilst separable in most cases, are mainly identified using features on the legs and back of the head that are rarely visible in photographs. So, most photographs can only be assigned to P. clypeatus sl. with any confidence. We may want to check records based on specimens.
Platycheirus peltatus/nielseni/amplus – males can be separated relatively simply from leg characters but females are a lot trickier. We suspect a lot of southern records of P. nielseni are misidentifications based on misinterpretation of the widths of tergite 2. Photographic records of this complex should be logged as P. peltatus sl. We may want to check records based on specimens.
Sphaerophoria – are mostly only seperable based on their male genitalia. Females cannot be reliably separated. A few can be readily identified: male S. scripta, male and female S. loewi and S. rueppellii. Other males can be identified (with care) from the male genital capsule but females are much trickier. Until very recently females were regarded as too difficult to split to make reliable records, but in recent years keys have emerged. As yet, those keys have not been adequately tested by British specialists and there remains some uncertainty about their reliability. We have had to take a pragmatic view that until there is more experience amongst UK specialists, females should be logged as "Sphaerophoria sp." unless recorded by a specialist with requisite experience. Unfortunately, this severely limits what can be recorded.
Microdon mutabilis/myrmicae – as noted above, this complex can only be separated on characters of larvae/puparia, and from DNA. Some hints about identity can be discerned from the habitat, but as in many cases there is close juxtaposition of suitable wet and stony habitats, great caution is attributed to these records and the majority are logged as M. mutabilis sl.
Xanthogramma pedissequum/stackelbergi – this is a relatively recent split that can usually be made if there are photographs from several angles and if the top-down photograph is of good quality. However, a sizeable proportion of photographs are too poor to make such an assessment and can only be assigned to X. pedissequum sl. There is a need for further caution, as X. dives has yet to be found in the UK but may well occur, either as a new arrival or lurking amongst existing populations.
There are several other problem areas where photographic records often cannot be assigned to a species. This is especially so in Heringia, Neocnemodon, Neoascia, Parhelophilus, most Sphegina, some Syrphus most Pipiza, Pipizella and Pelecocera caledonicus/scaevoides. In these cases, apart from a few exceptional (usually stacked) photographs or photos taken of critical features through the microscope, we assign these records at generic level.
It should be noted that whilst some Syrphus can be recognised from photographs (female S. ribesii from a side view showing the hind legs, male S. torvus and some female S. torvus where the photo is good enough to show eye hairs) the angle and quality of the photograph can be very important. We see innumerable photographs of males ascribed to S. ribesii or S. vitripennis that cannot be identified to species level with any confidence, and of females with no obvious eye hairs ascribed to S. vitripennis where the photo is not good enough to make this call. At the moment we record these as Syrphus sp.
Many species have quite refined habitat associations or geographic ranges. If a record is accompanied by a photograph, it is easier to verify, but if it comes from an unknown source some additional checks need to be made. Transcription errors are common and occasionally, we detect what might be ‘ringers’! Geographic range is often a useful way of screening out misidentifications where there is no accompanying photograph.
Grid reference errors are very common! They range from transposition of eastings and northings, to use of the wrong two-letter 100-km square prefix (or omission of that prefix), to incorrectly shortening the numerical section from the 10 figures that a GPS app may well provide to a more appropriate 4- or 6-figure grid reference. Records apparently from the sea somwhere off the coast are common because of these sorts of mistakes! The combination of a location name that can be found on a map, together with the Vice County helps us to validate the grid refererence.
The Ordnance Survey provide a useful guide to using grid references.
Whilst hoverflies flying at late or early dates do occur occasionally, many species have well defined and remarkably short emergence periods. This restricted timeframe is especially clear in spring species. So, for example, late summer records for a species that emerges and flies in April are likely to be wrong!