In this data paper, we describe two datasets derived from two sources, which collectively represent the most complete overview of butterflies in Flanders and the Brussels Capital Region (northern Belgium). The first dataset (further referred to as the INBO dataset – http://doi.org/10.15468/njgbmh) contains 761,660 records of 70 species and is compiled by the Research Institute for Nature and Forest (INBO) in cooperation with the Butterfly working group of Natuurpunt (Vlinderwerkgroep). It is derived from the database Vlinderdatabank at the INBO, which consists of (historical) collection and literature data (1830-2001), for which all butterfly specimens in institutional and available personal collections were digitized and all entomological and other relevant publications were checked for butterfly distribution data. It also contains observations and monitoring data for the period 1991-2014. The latter type were collected by a (small) butterfly monitoring network where butterflies were recorded using a standardized protocol. The second dataset (further referred to as the Natuurpunt dataset – http://doi.org/10.15468/ezfbee) contains 612,934 records of 63 species and is derived from the database http://waarnemingen.be, hosted at the nature conservation NGO Natuurpunt in collaboration with Stichting Natuurinformatie. This dataset contains butterfly observations by volunteers (citizen scientists), mainly since 2008. Together, these datasets currently contain a total of 1,374,594 records, which are georeferenced using the centroid of their respective 5 × 5 km² Universal Transverse Mercator (UTM) grid cell. Both datasets are published as open data and are available through the Global Biodiversity Information Facility (GBIF).

Butterflies, distribution, collection, literature, citizen science, observations, monitoring

INBO dataset: http://doi.org/10.15468/njgbmh

(http://www.gbif.org/dataset/7888f666-f59e-4534-8478-3a10a3bfee45)

Natuurpunt dataset: http://doi.org/10.15468/ezfbee

(http://www.gbif.org/dataset/1f968e89-ca96-4065-91a5-4858e736b5aa)

Butterflies are among the best studied insects in the world and have always attracted the attention of both professional researchers, amateur naturalists, butterfly collectors, and the wider public (Kühn et al. 2008). Butterflies are widely considered as interesting study systems for ecology, evolution, behaviour, and conservation biology (e.g., Watt and Boggs 2003). Many butterflies have been collected and subsequently stored in museum or private collections. Furthermore, entomologists have often published lists of observed species during excursions to special habitats or have made overviews of regional or national butterfly faunas. In Belgium, entomology in general and lepidopterology in particular, have a long tradition with the first faunas already published only seven years after its independence in 1830 (De Selys-Longchamps 1837). Since then, several authors have updated the Belgian butterfly fauna based on collections or observations (e.g., Hackray et al. 1969; De Prins 1998). In 1991, the youth and nature organization Jeugdbond voor Natuur en Milieu (JNM) launched a butterfly project with the aim to publish a distribution atlas of the butterflies of Flanders, northern Belgium (Daniëls 1991). To do so, a first step consisted of collecting all historical collection and literature data. Secondly, a working group was organised in cooperation between JNM, De Wielewaal (which later became Natuurpunt) and the INBO that set up a citizen science project to obtain as many butterfly observations with a good spatial coverage over Flanders. The data gathered during this project (period 1991-1998) were used to compile a first Red List (Maes and Van Dyck 2001) and a distribution atlas of butterflies in Flanders, including the Brussels Capital Region (Maes and Van Dyck 1999). Recently, both the Red List (Maes et al. 2012) and the distribution atlas (Maes et al. 2013) were updated using recent distribution data recorded through www.waarnemingen.be, a data portal launched by Natuurpunt, the largest nature conservation NGO in Belgium, where citizen-scientists can store and keep track of their recordings. Here, we publish both the historical and the more recent data used for the Red List and the distribution atlases as a data paper on a UTM grid cell resolution of 5 × 5 km².

The datasets cover all 67 indigenous and 3 regular migrant butterfly species (Colias croceus, Colias hyale, Vanessa cardui). In the INBO dataset vagrant or doubtful species (Apatura ilia, Arethusana arethusa, Boloria dia, Brenthis ino, Coenonympha arcania, Colias alfacariensis, Colias palaeno, Cupido argiades, Danaus plexippus, Erebia aethiops, Erebia ligea, Erebia medusa, Hamearis lucina, Iphiclides podalirius, Lampides boeticus, Lasiommata maera, Limenitis populi, L. reducta, Lycaena dispar, Lycaena helle, Lycaena hippothoe, Lycaena virgaureae, Melitaea aurelia, Pontia daplidice) and introduced species (Cacyreus marshalli and Polyommatus damon) were excluded because no evidence of the observation was available. In the Natuurpunt dataset, however, eight vagrant species with photographic evidence, that most likely spontaneously reached Flanders were included (Apatura ilia, Brenthis ino, Cupido argiades, Iphiclides podalirius, Lampides boeticus, Nymphalis xanthomelas, Polyommatus coridon and Pontia daplidice). Three additional species (Aporia crataegi, Argynnis adippe and A. aglaja) are considered as indigenous species, but recent observations are all vagrant individuals. Nomenclature is according to Fauna Europaea (http://www.faunaeur.org/full_results.php?id=7).

Kingdom: Animalia

Phylum: Arthropoda, Subphylum: Hexapoda, Class: Insecta, Order: Lepidoptera, Superfamilies: Hesperoidea, Papilioidea, Families: Hesperiidae, Lycaenidae, Nymphalidae, Papilionidae, Pieridae, Subfamilies: Apaturinae, Coliadinae, Dismorphiinae, Heliconiinae, Heteropterinae, Hesperiinae, Limenitidinae, Lycaeninae, Melitaeinae, Nymphalinae, Papilioninae, Pierini, Polyommatinae, Pyrginae, Satyrinae, Theclinae, Genera: Aglais, Anthocharis, Apatura, Aphantopus, Aporia, Araschnia, Argynnis, Aricia, Boloria, Callophrys, Carcharodus, Carterocephalus, Celastrina, Coenonympha, Cupido, Cyaniris, Erynnis, Euphydryas, Favonius, Gonepteryx, Hesperia, Heteropterus, Hipparchia, Issoria, Lasiommata, Leptidea, Limenitis, Lycaena, Maniola, Melitaea, Melanargia, Nymphalis, Ochlodes, Papilio, Pararge, Phengaris, Pieris, Plebejus, Polygonia, Polyommatus, Pyrgus, Pyronia, Satyrium, Spialia, Thecla, Thymelicus, Vanessa

Species: Table 1 gives an overview of the species, together with the number of records present in the respective datasets.

Common names: Butterflies

50°40'48"N to 51°30'36"N latitude, 2°32'24"E to 5°55'12"E longitude

All distribution data of butterflies in Flanders and the Brussels Capital Region were attributed to grid cells of 5 × 5 km² of the Universal Transverse Mercator (UTM) projection (Figure 2). The centroids of the 5 × 5 km² grid cells were calculated using the WGS84 projection with a coordinateUncertaintyInMeters of 3,769 meters (Wieczorek et al. 2004).

Figure 2. 

10 × 10 km² UTM grid cells in Flanders and in the Brussels Capital Region. The partitioning of 10 × 10 km² UTM grid cells (left) into 5 × 5 km² UTM grid cells is shown on the right. The 5 × 5 km² UTM grid cells were used to georeference the distribution data in Flanders and the Brussels Capital Region.

In total, Flanders and the Brussels Capital Region cover 638 (622 with records) and 9 (all nine with records) grid cells, respectively. The grid cells without records only cover a very small area within Flanders.

The INBO dataset mainly covers the historical museum and literature records (since 1830), butterfly monitoring records (since 1991) and observations (until 2008) while the Natuurpunt dataset covers the recent observations (mostly since 2008). Between 2000 and 2006, a butterfly survey project was organised in the province of West-Flanders (Cuvelier et al. 2007) and in the period 2006-2008, a similar project was undertaken in the Brussels Capital Region by the INBO on demand of Leefmilieu Brussel – BIM (Beckers et al. 2009). Both datasources were integrated in the INBO dataset. Since the introduction of the data portal www.waarnemingen.be for storing observations by the NGO Natuurpunt in 2008, the number of records has strongly increased and now reaches almost 150,000 records per year (Figure 3). The datasets will be updated on a yearly basis.

Figure 3. 

Number of collected records between 1830 and 1985 (left) and between 1986 and 2014 (right) in the two datasets (INBO and Natuurpunt). Each number on the x-axis stands for a period of 5 years (e.g., 1905 = 1901–1905, 1910 = 1906–1910, etc.). Note the different scales on the y-axis for both figures.

First of all, we would like to thank the many volunteers for their observations, the subsequent board members of the Vlinderwerkgroep for their contributions to different data collection projects. A list of contributors to this datapaper can be send on request for the INBO dataset and can be found on http://waarnemingen.be/ranks_abs.php?jaar=0&diergroep=4 for the Natuurpunt dataset. Gert Van Spaendonk, Pieter Vandenbroeck, Jo Loos, Tom De Boeck, Wouter Van Schandevijl, Frederic Piesschaert, Sven Schelfaut, Stijn Van Hoey and Filiep T’jollyn helped to build, maintain and use the INBO web application. Stichting Natuurinformatie build the data portal www.waarnemingen.be. We also thank Marc Pollet and Anne Eskildsen for useful comments on the manuscript.