Bombylius major

Bombylius major, the large bee fly, is a fly which is a bee mimic. It is a parasitoid on bees and wasps. The eggs are flicked by the adult female toward the entrance of the underground nests of solitary bees and wasps. After hatching, the larvae find their way into the nests to feed on the grubs.
They can be found in April to June in Europe and North America and some parts of Asia.