Not all flies are "bad," this robber fly is dining on a bot fly. Summer is waning and it's time for the adult robbers to show their rapacious heads. They have been growing up in dung heaps, soil and leaf debris, and compost piles, devouring anything that tasted good.
Fortunately, these robbers are not as big as house cats, if they were, you wouldn't be safe walking or riding your bikes on forest and desert trails. In fact, most people don't even notice them as they go speeding by in pursuit of a tasty meal.
Moreover, they are fast! I sort of look at these robbers as Nature's F-16 Viper jets. What I'm talking about are Robber Flies, the ultimate flying predator of the insect world. Once they start after a meal, it is dead meat!
The photo above shows the "good" part of the world of Nature, "Good" being in human terms. The hapless insect that robber fly is sucking dry is a bot fly, which, as those with livestock know, is a bothersome insect.
Bot flies grow under the skin of mammals, (humans included) feeding on blood and tissue of their host. When the grub emerges to metamorphose into an adult, it leaves a gaping infected hole in the host's skin. Not a pleasant sight…