Introduction

Neuropterida, comprising Neuroptera (lacewings and allies), Megaloptera (alderflies, dobsonflies and fishflies) and Raphidioptera (snakeflies), is a small superorder of holometabolous insects that contains ca. 6,500 extant species and is distributed worldwide. In Ireland, neuropterid insects are relatively poorly investigated. To date there have been no fossil Neuropterida discovered in Ireland.

Ireland

The island of Ireland (Ireland and Northern Ireland), is situated to the west of Great Britain (England, Scotland, and Wales). The country of Ireland (also known as the Republic of Ireland) shares a border with, but is politically separate from, Northern Ireland, which is part of the United Kingdom (UK; England, Scotland, Wales, Northern Ireland). The main geographical features of the country are low central plains and coastal mountains, the highest of which is Carrauntoohil (Kerry district) at just over 1,000 metres above sea level. Ireland is situated within the temperate deciduous forest biome. The vast majority of the country was once covered with forest, but deforestation since the arrival of man has reduced the forest cover to 9% of the land area. Peatland makes up 17% of the land, however, the vast majority of land (70%) is currently used for agriculture (Eaton et al. 2008). Only a few pockets of native forest remain, for example, the hazlewoods on the Burren (Clare) and the oakwoods around the Lakes of Killarney (Kerry).

Ireland is divided up into 31 local authorities (Fig. 1), which almost align with the 26 traditional counties. The differences are that Dublin is divided into four authorities (Fingal, Dublin City, South Dublin, Dún Laoghaire–Rathdown) and Cork City and Galway City are each separate from their respective counties. The faunal lists in this work are organized by these local authority districts.

1. Fingal	17. Kilkenny
2. Dublin City	18. Waterford
3. Dún Laoghaire–Rathdown	19. Cork City
4. South Dublin	20. Cork
5. Wicklow	21. Kerry
6. Wexford	22. Limerick
7. Carlow	23. Tipperary
8. Kildare	24. Clare
9. Meath	25. Galway
10. Louth	26. Galway City
11. Monaghan	27. Mayo
12. Cavan	28. Roscommon
13. Longford	29. Sligo
14. Westmeath	30. Leitrim
15. Offaly	31. Donegal
16. Laois

Neuropterida in Ireland

To date, 35 species of Neuropterida have been confidently reported from Ireland, and one additional species – Chrysopa perla – requires further confirmation. These species belong to 16 genera and six families. The orders Megaloptera (one family) and Neuroptera (five families) are present, but to-date, no Raphidioptera have been found in Ireland. The Irish fauna contains a very small fraction of the diversity of the Neuropterida of Europe (397 species; U. Aspöck et al. 2015), and represents a subset of the species that occur in the neighbouring UK (77 species; Plant 2014).

There are many questions with regards to how the insect fauna colonized Ireland in postglacial times. Did the Pleistocene glaciation, where an ice sheet covered Ireland, wipe out the entire fauna? Did some elements of the fauna survive in refugia in or near Ireland? Did the fauna colonize Ireland from continental Europe via Britain? If so, was this via a Holocene land-bridge? Or from over the Irish Sea?

All of the Neuropterida species in the Irish fauna are found in Britain, and also in mainland European countries, such as France and Germany. The majority of species are also known in Spain, and the Scandinavian countries (Denmark, Norway, Sweden) (Oswald 2018). Therefore, it is most likely that the neuropterid fauna colonized Ireland from Europe, via Britain. This has also been suggested for butterflies (Dennis and Hardy 2018), dragonflies and damselflies (Harrison 2014), and other Irish insects (Speight 1986).

But how did they get to Ireland from Britain? There has been debate as to whether a Holocene (11,650 years ago) land-bridge existed between Britain and Ireland, which would have enabled ready floral and faunal migration between the two land masses. The existence of a land-bridge of this age has, however, been doubted. Edwards and Brooks (2008), who used computer simulations of relative sea-level changes combined with bathymetric and topographic data, found no support for the presence of such a land-bridge, with their reconstructions suggesting that Ireland and Britain were separated earlier in the Pleistocene (16,000 years ago). The pathways that existed before this would have only been used by faunal and floral migrants that were cold-tolerant, as Ireland still retained ice at that time (Edwards and Brooks 2008). Therefore, the neuropterid fauna probably arrived in Ireland via wind, water (e.g. wood rafting), or possibly by human transport. These methods have been suggested as the main modes of colonization for insects into Ireland generally (Speight 1986, Reilly 2008, Whitehouse 2006), and some neuropterids may be quite recent arrivals, for example Chrysoperla carnea (see Barnard et al. 1987).

With regards to the distribution and composition of the Irish Neuropterida, other than the presence of the Irish Sea as a barrier, factors such as climate and a lack of suitable habitats, may be important reasons why Ireland has fewer species than the UK. Ireland possesses fewer habitats than the UK, for example, sandy lowland heaths, chalk downlands, and high altitude montane habitats are absent. In addition, woodland that is dominated by common beech and small-leaved lime do not occur naturally (Harrison 2014). The climate of Ireland, while similar to Britain, differs in having higher mean winter temperatures, higher rainfall than most of Britain, and cooler summers compared to southern England. Ireland’s position at the extreme western fringe of Europe means that it has a different climate from most other European countries, especially due to the influence of the Atlantic Ocean.

Some neuropterid species that are found in Britain, but not Ireland, appear to have a predominantly southern distribution, which may represent a temperature preference, e.g., Coniopteryx lentiae, Hemorobius contumax, H. fenestratus, and Euroleon nostras (see Plant 1994). With these taxa, climate may be a factor restricting successful colonization of Ireland. Other species, e.g., Wesmaelius malladai, are found in the Scottish Highlands, a habitat not present in Ireland; therefore again possibly limiting successful colonization. Many of the species occurring in Britain are already at the western European limits of their distributions, so climatic and habitat factors may act to restrict colonization further west. A similar situation is observed in the dragonflies and damselflies of Britain and Ireland, for which it has been suggested that lack of suitable climate and habitat factors in Ireland are as important in limiting colonization success as distance barriers, such as the Irish Sea, are at limiting dispersal (Harrison 2014).

It is possible that Ireland once had a greater diversity of Neuropterida, before the mass deforestation of deciduous forests and other habitat destruction, which started after man came to the island (Hall 2011). This habitat loss may have led to the extinction of neuropterid species that favour woodland habitats. This pattern of extinction has also been recorded in other Irish insect groups (McCarthy 1986).

The conjectures above about the colonization and dispersal of Neuropterida in Ireland are difficult to test, and at this time are speculative. This is partially due to the fact that the neuropterid fauna of Ireland is poorly recorded (Barnard et al. 1987, Plant 1997), and also from the lack of evidence of sub-fossil neuropterids at important time periods. The poorly-recorded nature of Ireland’s fauna is reflected in a plot of known neuropterid diversity by district (Fig. 2). Several districts have no or very few recorded species (e.g., Limerick, Carlow, Tipperary, Longford, Cavan). Most other districts have species numbers ranging from five (Offaly) to 21 (Kerry). The number of Neuropterida collection records also varies greatly across the districts, ranging from 0 (Limerick) to 55 (Kerry). Because Ireland is so poorly recorded for Neuropterida, it is very possible that other neuropterid species are present, but not yet documented.

History of the Study of Irish Neuropterida

Early mentions of several Irish lacewings are found in Haliday (1857), who noted the presence of Chrysopa abbreviata (Fingal district), and Hagen (1858) and McLachlan (1868), who both mention the presence of Sisyra terminalis in the Lakes of Killarney (Kerry). At this time very little was known about the Irish neuropterid fauna, and there was some interesting speculation about what might be present in the fauna. For example, Hagen (1858) wrote: “I do not consider it beyond the possibility that Southern Ireland may possess an extraordinary Nemoptera Lusitanica”. Unfortunately, this species – now Nemoptera bipennis – is not to be found in Ireland, being present only in hotter places like Spain and Morocco. The first faunal list that included Irish Neuroptera and Megaloptera was compiled in the late 19th century by King (1889), who listed one species in one family of Megaloptera, and 21 species in four families of Neuroptera. King’s work stimulated the publication of several additional short notes that added or mentioned lacewing species, e.g., Morton (1892), Beaumont (1893), King (1900; which first recorded Psectra diptera from Ireland), and McLachlan (1903).

In 1910, King and Halbert published an updated list of Neuropterida in which they listed one species in one family of Megaloptera, and 28 species in five families of Neuroptera. There is also a doubtful record of Chrysopa perla contained in A. H. Haliday’s manuscript “Catalogue of Irish Insects” (preserved in the National Museum of Ireland). This species has not been found subsequently in Ireland, and its presence in the fauna requires confirmation. After the publication of King and Halbert the Neuropterida of Ireland received little attention for many years. In 1912 Halbert published the results of a survey of the Neuroptera of the Clare Island district (Mayo), listing 13 species in 4 families. In his monograph of British Neuroptera, Killington (1936, 1937) gave the then-known distributions of Irish Neuroptera to county level. After a hiatus of more than 30 years Irish Neuropterida were mentioned again in several short notes in the 1960’s and 1970’s (e.g., Stelfox 1969; Speight 1976, 1977, 1983; Barnard 1977 – who added the first record of Sialis nigripes; and Speight 1979 – who first recorded Hemerobius pini). O’Connor (1983) confirmed the presence of Chrysopa abbreviata in Ireland (it was previously known only from a brief note in Haliday 1857), and O’Connor and O’Grady (1990) discussed the distribution of Sialis nigripes in Ireland. There were also brief mentions of neuropterids in papers devoted to other topics, for example, O’Connor and Bracken (1978) in a study on Irish lakes, and O’Connor et al. (1990) in a publication on insect pests. In 1987 Barnard et al. published records of Irish Neuroptera contained in the collections of the National Museum of Ireland and the Smithsonian Institution, USA. That study yielded 50 new distributional records, and listed 21 species in five families of Neuroptera.

Eighty-one years after King and Halbert an updated list of Irish Neuroptera was published by Barnard et al. (1991). They reviewed the published Irish data and updated it with previously unpublished records. They listed 31 species in five families of Neuroptera. The distribution of the Irish fauna was later visually displayed in the maps of Plant (1994). The distributions of Irish species were also reported at country level in Plant (1997). In subsequent years, a couple of short notes added Coniopteryx borealis to the Irish fauna (O’Connor 2003), and a sixth specimen of Psectra diptera was recorded (O’Connor 2008). Most recently, an up-to-date list of Irish Neuropterida was given in “An Annotated checklist of Irish Hemiptera and small orders” by O’Connor and Nelson (2012). They listed two species in one family of Megaloptera, and 31 species in five families of Neuroptera. Since that checklist, there have been no further publications on Irish Neuropterida. The most recent checklist omits two species, Pseudomallada prasinus and Drepanepteryx phalaenoides. They treat P. prasnius as a synonym of Pseudomallada ventralis (as Dichochrysa ventralis) and they do not mention Drepanepteryx phalaenoides. Barnard et al. (1991) and Plant (1994, 1997) consider Pseudomallada prasinus (as Mallada prasina) to be a species separate from P. ventralis, and Plant (1994, 1997) notes the presence of D. phalaenoides in Ireland. These two species have been added to the faunal list herein.

Methods

The faunal lists herein are based primarily on the published literature. The principal distribution data were taken from previously published lists (e.g., King 1889; King and Halbert 1910; Barnard et al. 1987, 1991) and from the atlas of Plant (1994). Some additional records and locality data were added from the National Biodiversity Data Centre Ireland (https://maps.biodiversityireland.ie/). Taxon names contained in previously published literature have been updated to the taxonomy used in the Neuropterida Species of the World catalogue (Oswald 2018).