Blera fallax, the pine hoverfly or roodkapje, is a rare species of hoverfly normally associated with mature pine trees in Northern and Central Europe.

[6] The pine hoverfly larva, which are of the rat-tailed maggot type, normally develop in damp rot holes of felled or fallen pine trees, notably the Scots pine (Pinus sylvestris), though it will occur with other conifers.

Preference is for large stumps where there has been some heartwood softening by the fungus Phaeolus schweinitzii.

[7] In Scotland, attempts have been made on RSPB sites to create artificial rot holes in felled pine stumps.

[7] Media related to Blera fallax at Wikimedia Commons