Cheshire Wildlife Trust Heteroptera and Diptera surveys on the Manchester Mosses with PANTHEON analysis by Phil Brighton 32, Wadeson Way, Croft, Warrington WA3 7JS [email protected] on behalf of Lancashire and Cheshire Wildlife Trusts Version 1.0 September 2018 Lancashire Wildlife Trust Page 1 of 35 Abstract This report describes the results of a series of surveys on the Manchester mosslands covering heteroptera (shield bugs, plant bugs and allies), craneflies, hoverflies, and a number of other fly families. Sites covered are the Holcroft Moss reserve of Cheshire Wildlife Trust and the Astley, Cadishead and Little Woolden Moss reserves of Lancashire Wildlife Trust. A full list is given of the 615 species recorded and their distribution across the four sites. This species list is interpreted in terms of feeding guilds and habitat assemblages using the PANTHEON software developed by Natural England. This shows a strong representation in the sample of species associated with shaded woodland floor and tall sward and scrub. The national assemblage of peatland species is somewhat less well represented, but includes a higher proportion of rare or scarce species. A comparison is also made with PANTHEON results for similar surveys across a similar range of habitats in the Delamere Forest. This suggests that the invertebrate diversity value of the Manchester Mosses is rather less, perhaps as a result of their fragmented geography and proximity to past and present sources of transport and industrial pollution. Introduction The Manchester Mosses comprise several areas of lowland bog or mire embedded in the flat countryside between Warrington and Manchester. They include several areas designated as SSSIs in view of the highly distinctive and nationally important habitat, such as Risley Moss, Holcroft Moss, Bedford Moss, and Astley Moss. Collectively these sites have also attracted the European designation of a Special Area of Conservation (SAC). Historically this environment covered a much a larger area1, including Chat Moss which was a major challenge to the construction of the world’s first public passenger railway between Liverpool and Manchester in the early 19th century. Much of the land has been drained for agriculture. The remaining bogs have been changed by peat cutting, with the exception of Holcroft Moss: even here however the raised bog is bordered by deep drainage ditches which draw down the water table. These activities and possibly other influences such as industrial air pollution have decreased the Page 2 of 35 extent of Sphagnum and other bog specialist plants, and much of the remaining non-cultivated area is dominated by Molinia and birch. In the most extreme cases industrialised peat extraction left large expanses of dry bare peat. Over the past two decades the Wildlife Trusts have acquired several of these sites and undertaken works to restore wetter conditions and counter the effects of past degradation. These works include the blocking of drainage ditches, installation of peat and plastic water-retaining bunds, and clearance of successional scrub growth, principally birch which accelerates drying of the ground through transpiration. As with any modern nature conservation scheme, ongoing surveying and monitoring of the flora and fauna is an important part of assessing the effects of the land management, identifying species of particular conservation concern, and learning lessons which may be applicable elsewhere. In 2009/2010, Lancashire Wildlife Trust (LWT) commissioned a comprehensive survey of the invertebrate fauna of Astley Moss SSSI by the World Museum Liverpool (WML)2. This survey has been used as a baseline to assess the results of further amateur recording of two insect groups, the terrestrial heteroptera and selected families of diptera in two previous reports3,4. This recording was started in 2012 to provide data for national recording schemes, but it was also hoped that it might be useful for monitoring variations and changes in the local environment arising from nature conservation activities, and also as a contribution to the general understanding of the local ecology. The previous reports concluded that the surveys had already contributed significant extra data to the WML survey. It was recommended that the surveys should be extended to cover Little Woolden Moss, a large tract subject to industrial peat extraction before it was acquired for restoration as a nature reserve by LWT in 2012. In addition to Astley Moss the previous surveys had covered Cadishead and Holcroft Mosses. All the sites were familiar to the author through involvement in voluntary conservation work. They all lie within the Watsonian vice-county 59 (South Lancashire) though Holcroft is now within the modern boundaries of Cheshire under the stewardship of Cheshire Wildlife Trust. Methodology and scope of recording The collecting technique used in 2012 and most of the 2013 season was sweeping with a net and capture in individual pots (30mm diameter and 50mm length approximately). In late summer 2013, this equipment was enhanced by acquisition of an aspirator, for use with screw-top collecting tubes of 50ml volume and 30mm diameter, and an 18” beating tray. On a full day’s survey, 12 tubes would be used, each numbered and recorded for a single six-figure grid reference. More than one tube would be used in particularly productive locations. The aspirator was used reasonably successfully to select only species from the target groups of interest (see below). The number of specimens per tube was limited to avoid damage, and would vary according to their size. Where fly specimens were well settled on flowers or leaves but could not be Page 3 of 35 identified in the field, pots were used to capture them individually – not always successfully. The pots were also needed to secure large craneflies and calypterates captured in the net. Bugs were collected largely in the same fashion, with the addition of beating of shrubs and the foliage of trees onto the beating tray or into a sweep net. Captured specimens were killed by storage in a freezer for a few hours at least or for several days at most. Following defrosting the specimens were pinned and staged in the case of flies, or with the bugs simply placed on Plastazote squares for identification under a low-power binocular zoom microscope. Typically 2-3 days’ effort was needed to identify a full batch. All the data from these survey have been recorded in a standard format with the following fields: Recording Scheme (see below) Species Date Site Location details (an indication of habitat if different from the site as a whole) Grid reference Vice-county Observer Determiner Sex Stage (Adult or nymph) Abundance Comments They were stored on Excel spreadsheets and submitted in that form to the recording scheme organisers and the Cheshire local records centre (rECOrd) up to the end of 2016. Records from 2017 onwards are being uploaded to the IRECORD site developed by the Biological Records Centre. Here they are available to local records centres and to national recording scheme verifiers, as well as being immediately visible to other IRECORD users. Table 1 summarises the extent of the surveying according to month of the year and the four sites. As previously a single record denotes the detection of a species on a particular day in a single 100m square. On each site a fairly consistent route was taken to cover the variety of habitats present, which mostly included Molinia-dominated mossland, heathland, and birch and willow woodland. Marginal areas such as tall herbage along entrance tracks or scrub at the edge of woodland was also sampled, being often the most productive areas. Details of these habitats are included in the records as noted above. Cadishead Moss is essentially an extension of Little Woolden Moss, so they were covered as a combined unit for these surveys, but the results have been separated because of the different nature of their dominant habitats. The figures in Table 1 are essentially an indication of the total recording effort: no inference should be drawn about the relative abundance of insects beyond the obvious one that they are scarcer in the winter months. The figures show that the sampling across the sites and seasons has not been entirely consistent, having been part of a wider evolving programme covering other sites and habitats in Lancashire and Cheshire. The surveys at Cadishead and Little Woolden Moss started rather later and have lagged behind. There has been an unaccountable neglect of Astley Moss in August and of Holcroft Moss in July. However, the results Page 4 of 35 of the PANTHEON analysis given below do indicate that there is sufficient data on each site to give meaningful results. Table 1: numbers of records by calendar month and site Month Astley Moss Cadishead Holcroft Little Woolden Totals Moss Moss Moss January 1 1 February 21 48 69 March 175 54 86 40 355 April 51 81 161 36 329 May 108 69 303 31 511 June 155 79 202 135 571 July 371 138 72 120 701 August 4 63 285 57 409 September 250 1 348 599 October 132 4 356 492 November 10 7 17 December 2 4 6 Totals 1278 491 1872 419 4060 It should be noted that many of the records in this report are yet to be verified by the local recording centres or national recording schemes. Species Recorded Tables 5a-f at the end of the report give full details of the numbers of records for each species across the four sites, divided into six groups, as follows: Terrestrial Heteroptera (Table 5a) This group includes the shieldbugs, and the plantbugs and allies. The British Bugs website (www.britishbugs.org.uk) provides an authoritative guide to these and also covers aquatic heteroptera. A couple of genera from the latter (Chartoscirta and Saldula) are also included in the surveys as they have a predominantly terrestrial lifestyle and so are encountered in sweep-netting.