Les Cercyon sont de petits Hydrophilidae surtout terrestres, mais semi-aquatiques pour quelques uns. C. rhomboidalis fait partie de ceux-ci et appartient au sous-genre Cercyon, le plus nombreux du genre en Europe. Avec un dessus brillant, des élytres plus clairs que le pronotum et des interstries élytraux convexes, l'insecte présente, à la face ventrale, une apophyse mésoventrale en ovale très élargi, séparée du métaventrite par un léger espace. Associée à la petite taille de l'insecte et à son habitat, cette conformation très particulière est propre à l'espèce et suffit à l'identifier.
Détermination :
Moyennement difficile sur photo d'ensemble.
Espèces proches :
Malgré sa petite taille, C. rhomboidalis possède des caractères très distinctifs parmi le genre Cercyon et observables relativement facilement, ce qui diminue le risque de confusion avec d'autres espèces.
Période d'observation :
Adulte rencontré presque toute l'année.
Biologie-éthologie :
Matières végétales en décomposition, en zone marécageuse découverte, au pied des plantes basses et de la mousse.
Biogéographie et écologie :
Espèce peu fréquente dans son aire de répartition limitée aux îles sardo-corses.
Queney P. et Prévost P. 2021. Clé d'identification des Coléoptères aquatiques de France métropolitaine Myxophaga, Polyphaga Hydrophiloidea (adultes). Tome 1.
The map presents a summary at the 10 x 10 km grid of the observation data for the species transmitted to the SINP. These data have been subjected to validation filters.
Distribution map from the Atlas of Departmental Biodiversity and Marine Sectors program
Current distribution in metropolitan France
The map presents a reference distribution layer of the species at the scale of departments and marine sectors. The presence and absence data were established by expertise within a network of partners. This reference distribution is used in the validation process of the SINP data at the INPN level.
Distribution map from the Atlas of Departmental Biodiversity and Marine Sectors program
Certain presence
Corresponds to a report on the basis of at least one observation proved within a period of 10 years (20 years for little-known invertebrates) preceding the year and no presumption of extinction since obtaining the last data nor doubt on reproductive and implemented nature of this population. For migratory species, the presence indicated concerns areas of reproduction.
Probable presence
This status is based on one or more of the following criteria:
search of species incomplete but presence of supportive environments;
ecology of the species consistent with the hypothesis of his presence;
the last reliable sighting is older than 10 years compared to the reference date, no recent specific research and no presumption of extinction from that date [vertebrates, invertebrates and plants well studied (rhopalocera, grasshoppers, dragonflies ...)] ;
the last reliable observation being older than 20 years, no recent specific research and no presumption of extinction from that date [poorly known taxa: fungus, many invertebrates...].
Probable or certain absence
This point covers the absence, more difficult by nature to demonstrate than presence. This status is based on one or more of the following criteria:
intensive but unsuccessful targeted research;
lack of adequate environments;
unobserved species while its presence is easily detected;
unlikely presence for historical or biogeographical reasons.
This status must be assigned to a department in which the presence of the species is casual.
Absence due to a proven extinction
Particular case of absence due to a proven extinction less than a half century ago (older disappearances are treated as "no probable or definite").
No information
In the state of knowledge, we can not comment on the presence or absence in the current department. This is the default status when not comprised in one of the previous categories or whenever there is doubt.
French Version
