Dolichopodidae checklist for VCs 58, 59 & 60

(c) Rod Hill

Notes on the Dolichopodidae species checklist

  1. The checklist covers the species of the family Dolichopodidae (long-legged flies) of vice-counties: 58, 59 and 60, which is essentially Lancashire and Cheshire.
  2. It is based on a total of nearly 11,400 records stored in a database that has been compiled from a wide range of sources e.g. individual recorders, iRecord (incorporating iNaturalist), rECOrd, Merseyside BioBank, Lancashire Environment Record Network, Greater Manchester Local Records Centre and the Empididae, Hybotidae & Dolichopodidae Recording Scheme.
  3. It has been supplied as a spreadsheet, showing combined details for all three vice-counties, with three extra worksheets providing a checklist for each individual vice-county. These are accessed by clicking on the relevant tab at the bottom of each worksheet. The latest figure for the total number of Dolichopodidae species in the British Isles currently stands at 308 (Chandler, P.J. Checklist of the British Diptera of the British Isles, updated on 28 July 2021).
  4. As with the hoverfly checklist published a few years ago, this checklist is provisional and should not be taken as a definitive reflection of the actual state, either past or present, of this family of flies in the three vice-counties. It is simply a ‘first attempt’ to give all concerned an indication of the species that have been previously recorded in these vice-counties.
  5. As such, it is acknowledged that the current database contains many duplicates, questionable records (mainly because existing keys are not correct for some genera and species) and not all existing records have been harvested. The last point is especially true for records obtained from the national recording scheme, which has not been able to export records for about the last 18 months due to a computer software problem. This, I suspect, will not have a major effect on the checklist, as most Diptera recorders in Lancashire and Cheshire now use iRecord and I have harvested all relevant records entered into their database up to the end of May 2022.
  6. Much effort has been put into producing new keys, especially by Martin Drake of the national recording scheme, and these, when available, will make a marked improvement on correct future identification. As the checklist is an ongoing project, it will hopefully, in time, evolve into a more accurate representation of the true situation.
  7. There are two columns in the checklist that indicate the future threat to the species and their current rarity status in Britain. The first column is one based on the International Union for Conservation of Nature (IUCN) system, which grades the threat posed to the future survival of a species. Below are the applicable categories in order of decreasing threat:

Regionally Extinct/Critically Endangered/Endangered/Vulnerable/Near Threatened/Least Concern/Data Deficient/Not evaluated.

The second column is a simplified version of the categories specified in the Red Data Books system that was developed specifically for British species. It contains only two specified categories:

Nationally Rare. This applies to native species that have been recorded from 15 or fewer hectads of the Ordnance Survey National Grid in Britain.

Nationally Scarce. This category is applied to native species that have been recorded in more than 15 hectads but not more than 100 hectads.

Any species having been recorded in more than 100 hectads are not categorised and are shown as a blank in the column.

These two categories have been used to add clarity to the status of a species because being rare does not necessarily mean that a species is under threat of extinction. Some species are rare but have stable populations. They may have always been rare and may continue to be so.

The appropriate updated values of these two categories were obtained from Drake, C.M. 2018. A review of the status of the Dolichopodidae flies of Great Britain – Species Status No. 30. Natural England Commissioned Reports, Number 195.

The above publication is available to download as a pdf document from a number of locations on the Internet and is recommended for further information/study and for more sophisticated threat assessment than is possible in my simplified checklist.

  1. Finally, as always, I would like to thank all the individuals and organisations concerned for their kind assistance in providing relevant records and the Tanyptera Project for making the checklist available to the public.

Glenn Rostron (30 June 2022).

Download Now