The status and distribution of the horseflies Atylotus plebeius and Hybomitra lurida on the Cheshire Plain area of North West England

Summary

This document is a report of the findings of a broad-ranging survey carried out by Andrew Grayson [the surveyor] during summer 2018 on numerous mire habitats and related wetlands throughout the Cheshire Plain area.

The main focus of the survey was the diminutive horsefly Atylotus plebeius (Fallén, 1817), which was appropriately given the vernacular name Cheshire Horsefly by Stubbs & Drake (2001 & 2014), as its British distribution seems to be restricted to Cheshire Plain mires. Its British status was given as Nationally Rare in the recent status review by Drake (2017). Its International status [designated by IUCN – International Union for Conservation of Nature www.iucnredlist.org] is considered Endangered.

The second main target of the survey was Hybomitra lurida (Fallén, 1817), the Broad-headed Horsefly of Stubbs & Drake (2001 & 2014). This horsefly is widely distributed in Scotland, but its English distribution is apparently restricted to the Cheshire Plain area. Its British status was given as Nationally Rare by Drake (2017). Its IUCN International status is Vulnerable.

Although not stated within the main title of this report, the surveyor’s third target horsefly was Tabanus maculicornis Zetterstedt, 1842. This relatively small clear-winged horsefly was correctly recognised as being Nationally Scarce by Drake (2017), and was given the vernacular name Narrow-winged Horsefly by Stubbs & Drake (2001 & 2014). Its IUCN International status is Least Concern.

Prior to the survey of 2018, none of these three aforementioned horseflies had been recorded from the Cheshire Plain area since the 20th Century, so any findings during 2018 would be interesting, particularly any re-discoveries of Atylotus plebeius.

As the main target horseflies Atylotus plebeius and Hybomitra lurida breed on bogs, the surveyor aimed to visit as many Cheshire Plain area mires as was feasibly possible during the summer of 2018, and to target mires and other wetlands whence these national rarities had previously been recorded; and, more especially, any mires which were, at least in part, quaking bogs; regardless of whether Atylotus plebeius or Hybomitra lurida had previously been recorded there. The constraints would merely be the availability of the surveyors’ time, suitably hot and sunny weather conditions, and gaining the necessary permissions from various landowners to carry out surveying.

It was inevitable that other horseflies [Tabanidae] would be encountered during the course of the survey. These would always be recorded, as this report aims to provide an assessment of the current status and distribution of all Tabanidae on Cheshire Plain area mires, based on the 2018 study.

It was also inevitable that many other invertebrates would be encountered during the course of the survey, including some which were captured by Manitoba traps which were left in situ throughout the survey period on four sites. This report includes all data from incidentally-encountered invertebrates which were captured by the surveyor for critical analysis, plus those captured by the aforementioned traps, and including all conspicuous and easily-identifiable invertebrates which were identified in the field.

The surveyor intends to forward the majority of specimens taken during the course of the survey to the World Museum, Liverpool, in order that they can be added to the collections and provide vouchers for the records within this report.

Where thought necessary, this report also aims to provide recommendations on current and future management of Cheshire Plain mire sites, and identify any significant or adverse management issues.

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