Yellow-margined sap beetle
Cyllodes ater
The yellow-margined sap beetle is a small, 3.5 to 5 mm long beetle with a strongly convex and shiny black body. It is characterized by the yellowish or reddish translucent margins of its pronotum and elytra. This species belongs to the Nitidulidae family and is ecologically tied to the presence of oyster mushrooms (Pleurotus). It primarily inhabits damp deciduous forests with a high proportion of decaying wood.
Details
Identification
Hemispherical, highly convex body shape; deep shiny black; margins of pronotum and elytra often yellowish-translucent; antennae with a distinct club.
Social behavior
Often found in small groups on host fungi, otherwise largely solitary.
Diet
Mycetophagous; both larvae and adults feed on the mycelium and fruiting bodies of fungi.
Spawning substrate
Fruiting bodies of wood-decaying fungi, especially oyster mushrooms (Pleurotus).
Overwintering
Overwinters as an adult in leaf litter or under loose bark.
Ecology
Ecological role
Part of the saproxylophagous community; contributes to the decomposition of fungal fruiting bodies in forest ecosystems.
Natural predators
Insectivorous birds, assassin bugs, predatory beetles (e.g., rove beetles), and spiders.
Competitor species
Other mycetophagous beetle species, such as members of the family Erotylidae (pleasing fungus beetles).
Ecosystem service
Support of the nutrient cycle through the decomposition of fungal biomass.
Threats
Intensive forestry leading to the removal of dead wood and the loss of host fungi.
Scientific profile
Profile
Distinguishing features
Body almost hemispherically convex and glabrous. The antennae have a prominent, three-segmented club. A characteristic feature is the strongly widened tibiae of the legs. The species differs from related genera through the combination of a smooth surface and specific marginal coloration.
Habitat
Old-growth mixed deciduous forests, especially old beech forests with high proportions of deadwood. The species is obligately associated with fungi of the genus Pleurotus (oyster mushrooms, e.g., P. ostreatus and P. cornucopiae) growing on weakened or dead deciduous trees.
Diet
Mycetophagous (fungivorous); both larvae and adults specialize in feeding on fungi of the genus Pleurotus.
Role in food web
Primary consumer (mycetophagous); serves as prey for predatory beetles (e.g., Staphylinidae) and insectivorous birds.
Protection & threats
Status not on standard scale
Main threats
Intensive forestry leading to the removal of old and dead wood; loss of habitat trees with fungal growth; fragmentation of near-natural forests.
Population trend
Regionally listed on the Red List in Germany (e.g., Bavaria: RL 3 - endangered) or the early warning list; populations are highly dependent on the availability of suitable fungal substrates.
Conservation measures
Preservation of old and dead wood (especially beech); protection of trees infested with oyster mushrooms; promotion of process protection in forest reserves.