Inventories and surveys have revealed the presence of 45 species of butterfly and 27 species of Orthoptera. Some of them appear on the Alsace red list, including: the Dryad and the Short-tailed Blue, the Brown-spotted Bush-cricket, the Steppe Grasshopper and the Green Leek Grasshopper. The most remarkable species in terms of rarity and protection status is the Large Copper.

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Principle of the surveys of entomofauna carried out in the reserve

The heritage entomofauna in open habitats in the National Nature Reserve presents species that can be qualified as indicative in view of the habitats they occupy. They may thus be dependent on the structure of the habitat in question as for Orthoptera (tall or low herbaceous layer, visible mineral substrate…) or its specific floristic composition, particularly for Lepidoptera related principally to a host plant.

By monitoring indicative species, it is a question of visualising the development, health and quality of the open habitats and, therefore, assessing the efficacy and relevance of the management operations conducted on them.

Several habitats in which indicative heritage species are present or likely to be so are covered by "transects" along which the populations present are noted either by direct identification (visual and/or auditory identification) or by being captured in nets (and released afterwards). The operation is carried several times in all of the habitats concerned throughout the summer period (May to August).

Species monitored

The main heritage species monitored and their specific habitats are the following:

Brown-spotted Bush-cricket (Platycleis tesselata) and Grey Bush-cricket (Platycleis albopunctata):

These two species of grasshopper appear in the Red List Alsace – Vulnerable and the Orange List Alsace – To be monitored.

The Grey Bush-cricket is generally well represented right across the reserve in all habitats favourable to the species: thermophilous habitats along the dykes and grassland or dry xerophilous meadows on gravel situated at the entrance to the reserve (or even on top of dykes).

The Brown-spotted Bush-cricket (the rarer of the two species) is considerably less in evidence on the site as only one population (+/-30 individuals) subsists along the high water dyke. Here, the species finds a habitat similar to the one sought by the Grey Bush-cricket, but with a much denser plant component at ground level.

With time and experience, specific identification can be done by sight or hearing for the Grey Bush-cricket, but for greater certainty and to obtain sex ratio information, for example, netting is necessary.

Steppe Grasshopper (Chorthippus dorsatus) and Green Leek Grasshopper (Mecostethus parapleurus):

The first appears in the Red List Alsace – In decline, the second in the Red List Alsace – Vulnerable…

The first is widely represented right across the reserve in all open habitats and the second has been present on the site for only a short time (since 2010), in a few small populations (4 isolated populations) of 1 to 10 individuals maximum. Both species seek out tall herbaceous plant formations on the site, or even relatively warm to humid habitats. Within certain communities of Orthoptera, they are considered companion species.

With experience, the Green Leek Grasshopper can be easily observed/identified by its size and colouring on the ground or in flight. The Steppe Grasshopper is difficult to identify unless captured (in order to be able to differentiate it with certainty from other closely related species) but has a particular call which eliminates any doubt as to its identification.

Dryad (Minois dryas):

This species appears in the Red List Alsace – Vulnerable. It seeks out dry grassland on the reserve, which can be found at the entrance to the site and along the dykes and in tall herbaceous meadow formations with variable hydric conditions composed principally of Graminaceae on which it lays its eggs. Identification of the species by sight is easy, whether still or in flight.

Large Copper (Lycaena dispar):

This is the only butterfly species that enjoys national protection found on the reserve. It also appears in the Red List Alsace – In decline and in Annexes II and IV of the Habitats Directive. The species is linked to humid meadow and, more particularly, to the presence of the host plant necessary for egg-laying and the development of larvae, Curled Dock (Rumex crispus) in particular. The imago (adult butterfly) too is linked to the presence of this species, but the range of species sought out for their nectar is broader: Common Fleabane (Pulicaria dysenterica), Hemp Agrimony (Eupatorium cannabinum), Purple Loosestrife (Lythrum salicaria)… Identification of the species can be done by sight, still or in flight, but to avoid any confusion with a similar species and obtain sex ratio information, for example, netting is necessary.

Photographs:
Brown-spotted Bush-cricket © Camille HELLIO
Grey Bush-cricket © Camille HELLIO
Green Leek Grasshopper © Camille HELLIO
Male Dryad © Camille HELLIO
Male Large Copper © Camille HELLIO
Short-tailed Blue