Its nickname is assassin fly but, you are not in danger, it eats other insects. It does bite. Its bite is painful to humans, but they bite only when provoked. To other insects bees, butterflies, grasshoppers, beetles, and other flies-the robber fly is deadly.
In Latin this insect belongs to the family Asilidae. Approximately 1,000 species of Asilidae have been discovered in North America. Perhaps you’ve heard of robber flies. If not, you should know about them.
Robber flies are true predators in the insect world. From the larval stage produced from an egg laid on a low plant, or even in the soil a robber fly larva emerges to eat its way to adulthood. The way it eats is remarkable. The way it over winters as a larva in the soil is more. It freezes, yet lives on. The larva pupates in the soil. This stage can take from 1-3 years depending on the species of robber fly and the environment where it is found.
Why become excited about a robber fly? If overwintering in frozen soil does not impress you, its hunting prowess should. It captures its prey on the fly. Watch a bumblebee or butter fly, or even the lowly house fly. Attempt, if you can, to follow its flight for more than a second. Robber flies not only follow, they intercept these flying insects midair. Using exceptionally acute vision generated by their large compound eyes, they target their prey inflight with unfailing accuracy. Yes, it’s astonishing. There’s a problem though, robber flies are usually smaller than their prey. Now for the amazing.
Robber flies have long powerful, and bristled grasping legs. But, not strong enough to hold an insect larger than it is. Yet, just strong enough to hold the insect while the robber fly injects it with poisonous venom. Robber fly venom contains neurotoxic and proteolytic enzymes. Think of it as a small dose of snake venom. In milliseconds this venom kills and liquefies the insides of the insect. The robber fly then perches on a nearby plant and consumes a liquified meal of insect parts and venom-but it lives!
An eternal reason to know about the robber fly it defies every human explanation for its existence.
Consider these facts you know:
- It kills other insects, yet the balance of insect life on earth is maintained.
- Exceptional vision…able to catch other flying insects in air! Its sight and instinct combined.
- Insect killing venom…that does not kill the robber fly, an insect itself.
- 1,000 species in North America, over 7,000 worldwide, each different, yet robber fly.
These attributes point us to the true origin of the robber fly, a Creator. Consider the questioning words of the prophet Isaiah who asked, “Do you not know? Have you not heard? The Lord is the everlasting God, the Creator of the ends of the earth. He will not grow tired or weary, and his understanding no one can fathom.” (Isaiah 40:28) A small, but amazing part of the “ends” of the earth is the robber fly. Its existence is unfathomable. You should know about it.
This more than about a fly. It’s about eternity. The robber fly points the way.