Bombyliidae

The Bombyliidae are a family of flies. Their common name is bee flies.
The Bombyliidae are a large family of flies. It has hundreds of genera, but the life cycles of most species are known poorly, or not at all. Some are very small (2 mm in length), but some can be very large for flies (wingspan of some 40 mm).
Adults normally feed on nectar and pollen. Those with a spectacularly long proboscis are adapted to plants (such as "Lapeirousia") which have long, narrow floral tubes.
The Bombyliidae include a large number of species, but for its size this is one of the least understood families of insects. There at least 4,500 described species, and certainly thousands still to be described. The adult flies usually feed on nectar and pollen, and some are important pollinators.
Bee mimics.
Many Bombyliidae look like bees and so a common name for the family is the bee flies. The reason is probably aposematic: the adults are safer from predators because they share the warning colours of bees. The adult females usually lay eggs near the nests of possible hosts, often in the burrows of solitary bees, wasps or beetles.
Larvae.
The larval stages are predators or parasitoids of the eggs and larvae of other insects. The eggs hatch into larvae which eat the eggs and larvae of the 'host' insect. Although most bee-flies usually are fairly or highly host-specific, some species do attack a number of hosts.