Family Bombyliidae

Bodenheimer (Animal Life in Palestine, 1935) has this to say:
The Bombyliid flies are among the most characteristic of our insects. Their number is legion in the spring and early summer. Although they have not yet been collected intensively, more than 50 species are known up to date, and there is little doubt that their real number amounts to some hundreds of species. The genera Bombylius, Exoprosopa, Anthrax, Mulio, Usia etc., are best represented. On sunny days they are seen visiting flowers and are easily recognised by their wooly covering of hair and their long snout (up to 10 mm) and by the fact that they hover over the flower, but never alight on it at the time of their visit. The larvae are parasites on solitary bees and grasshoppers. The female drops the eggs on the soil. The hatching larva has three pairs of thoracic bristles with which it runs quickly over the soil until it finds the entrance to an egg-packet of grasshoppers or to a nest of bees.

From Wikipedia:
Bombyliidae is a large family of flies with hundreds of genera, although their life cycles are not well known. Adults generally feed on nectar and pollen, thus are pollinators of flowers. They superficially resemble bees, thus are commonly called bee flies, and this may offer the adults some protection from predators. The larval stage are predators or parasitoids of other insect eggs and larvae. The adult females usually deposit eggs in the vicinity of possible hosts, quite often in the burrows of beetles or wasps/solitary bees. Where most often in the insect world parasitoids are highly specific in the host species that they will infect, it is thought that bombyliids are opportunistic and will use a variety of hosts. While bombyliids have a great variety of species, rarely are individuals of any one species abundant, and this is perhaps one of the poorest known families of insects relative to its size. There are at least 4,500 described species, and probably thousands as of yet undescribed.

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