A bee fly (Bombylius sp.) hovers over a mountain jewel flower (Streptanthus cf. tortuosus) in Yosemite National Park. Bee flies are among the most adorable flies, very round and bumble-bee like, making a characteristic monotone hum as they hover in the air. As the fly sticks its elongated proboscis into the floral tube its hairy body is covered with pollen granules, eventually pollinating around the wildflower patch. Bee flies are capable of hovering motionless in mid-air much like hover flies (family Syrphidae), sometimes using their front legs to stabilize themselves on a flower. As larvae Bombyliids have diverse life histories. They are parasitoids of many insect clades including wasps, bees, flies, beetles, moths, grasshoppers, and neuropterans, and some taxa have been found to be pseudohyperparasitoids of ichneumonid wasps in Lepidoptera. In the genus Bombylius, adults will coat each egg with sand grains before laying or flicking the egg in the entrance of a suitable burrow of solitary bees or wasps. The first instar larvae have functional legs for crawling inside before molting and feeding on food reserves or the hymenopteran larvae themselves.
Photographed in situ / during pursuit [1-3]