Meetnetten.be - Transects for butterflies in Flanders, Belgium

Study Extent

1. Cyaniris semiargus (mazarine blue / klaverblauwtje) was once widespread, but now endangered, with only one known location. It is bound to grasslands with sufficient Trifolium pratense (red clover), its host plant. 2. Erynnis tages (dingy skipper / bruin dikkopje) in Flanders is limited to a handful of locations in Limburg. It prefers (calcareous) grasslands with Lotus corniculatus (common bird's-foot trefoil). 3. Hesperia comma (silver-spotted skipper / kommavlinder) can be found in a limited number of dry heathland areas with well-developed heather-rich vegetation. 4. Hipparchia semele (grayling / heivlinder) is mainly found on dry heathland, heather-rich grasslands and dunes with open sand, sheep grass or ostrich grass. 5. Lasiommata megera (wall brown / argusvlinder) lives in verges and grasslands. Its populations have deteriorated considerably in recent decades. 6. Melitaea cinxia (glanville fritillary / veldparelmoervlinder) can be found in barren grasslands with a sufficient number of Plantago lanceolata (narrow plantain). 7. Pyrgus malvae (grizzled skipper / aardbeivlinder) can be found in only a handful of locations in Flanders. It lives on nutrient-poor grasslands, with Potentilla erecta (tormentil) as host plant. 8. Pyronia tithonus (gatekeeper / oranje zandoogje) is a common species in Flanders that occurs locally in high densities. The distribution of this species is limited to Europe and in Western Europe Pyronia tithonus reaches high densities, but here and there the species declines: therefore this butterfly was selected as a Flemish priority species. 9. Euphydryas aurinia (Marsh fritillary) The marsh fritillary (Euphydryas aurinia) is a butterfly of the family Nymphalidae. Commonly distributed in the Palearctic region, the marsh fritillary's common name derives from one of its several habitats, marshland. The prolonged larval stage lasts for approximately seven to eight months and includes a period of hibernation over the winter.

Sampling

Sampling was done using the protocol described in Maes et al. (2019) and explained to volunteers in Ledegen et al. (2018). Cyaniris semiargus (mazarine blue / klaverblauwtje), Erynnis tages (dingy skipper / bruin dikkopje), Hesperia comma (silver-spotted skipper / kommavlinder), Melitaea cinxia (glanville fritillary / veldparelmoervlinder) and Pyrgus malvae (grizzled skipper / aardbeivlinder) occur in less than 30 locations in Flanders. For these species all locations are selected for monitoring and counted annually. Hipparchia semele (grayling / heivlinder), Lasiommata megera (wall brown / argusvlinder) and Pyronia tithonus (gatekeeper / oranje zandoogje) occur in more than 30 locations. For these species a random sample of 30 locations was drawn, which are counted once every three years. Within each selected location, transect counts are carried out. A fixed route of a maximum of 1000m is mapped out, along which the numbers of butterflies per section of 50 m are counted within an imaginary cage of 5 x 5 m around the observer. The sampling protocol may vary a little, depending on the butterfly species. 1. Cyaniris semiargus (mazarine blue / klaverblauwtje): the first generation flies in spring (May), the second generation can be found in high summer (10 July - 10 August). Both seasons are followed up in this monitoring network (at least three field visits per flying season). 2. Erynnis tages (dingy skipper / bruin dikkopje): flies in 2 generations, in spring (May) and in high summer (20 July - 20 August) and is therefore followed up in both seasons (at least six field visits). 3. Hesperia comma (silver-spotted skipper / kommavlinder): we ask at least 3 field visits in good butterfly weather, during the month of August. 4. Hipparchia semele (grayling / heivlinder): in a counting year we ask at least 3 field visits in good butterfly weather, in the period from 20 July to 20 August. 5. Lasiommata megera (wall brown / argusvlinder): in a counting year we ask for 6 field visits in good butterfly weather, 3 in May and 3 in the period from 20 July to 20 August. 6. Melitaea cinxia (glanville fritillary / veldparelmoervlinder): we ask at least 3 field visits in good butterfly weather, between 1 and 31 May. 7. Pyrgus malvae (grizzled skipper / aardbeivlinder): we ask at least 3 field visits in good butterfly weather, during the month of May. 8. Pyronia tithonus (gatekeeper / oranje zandoogje): in a counting year we ask at least 3 field visits in good butterfly weather, in the period from 15 July to 15 August. 9. Euphydryas aurinia (Marsh fritillary) : 3 visits a year in good butterfly weather (3 field visits in May)

Quality Control

Data are collected using a predefined sampling protocol.

Method steps

1. Researchers from INBO and Natuurpunt Studie define and document the appropriate sampling protocol for the target species.
2. Fieldwork is planned and coordinated by Natuurpunt Studie, using https://meetnetten.be.
3. Data are collected in the field by specialized volunteers, using the predefined sampling protocol.
4. Volunteers enter the collected data in https://meetnetten.be.
5. A custom SQL view is created in the meetnetten.be database to map the original data to Darwin Core as an event core and occurrence extension.
6. The Darwin Core views are connected to the INBO IPT and documented with metadata.
7. The dataset is published and registered with GBIF.

The target butterfly species for Meetnetten.be are listed at https://meetnetten.be/#group-4. Other butterflies observed during the sampling are also included. This dataset covers the transect protocol, for which there are 8 target species.

1. Animalia
   common name: animals rank: kingdom
2. Arthropoda
   rank: phylum
3. Insecta
   common name: insects rank: class
4. Lepidoptera
   common name: butterflies rank: order
5. Cyaniris semiargus
   common name: mazarine blue / klaverblauwtje rank: species
6. Erynnis tages
   common name: dingy skipper / bruin dikkopje rank: species
7. Hesperia comma
   common name: silver-spotted skipper / kommavlinder rank: species
8. Hipparchia semele
   common name: grayling / heivlinder rank: species
9. Lasiommata megera
   common name: wall brown / argusvlinder rank: species
10. Melitaea cinxia
    common name: glanville fritillary / veldparelmoervlinder rank: species
11. Pyrgus malvae
    common name: grizzled skipper / aardbeivlinder rank: species
12. Pyronia tithonus
    common name: gatekeeper / oranje zandoogje rank: species
13. Euphydryas aurinia
    common name: Marsh fritillary rank: species

Flanders, Belgium