This is what i found
Drone Flies
Drone flies are also called rat-tailed maggots due to their long breathing tubes. They are also called hover flies. I discovered drone flies in my tiny pond in the Fall of 1997. This pond can be seen here. Drone flies are readily identified by their long breathing tubes which look like a long string (1-2 inches) attached to their rear. They keep the tubes sticking out of the water to breath. Their bodies look like land maggots (the kind that make many female humans scream). They are only found in shallow water without predators (fishless ponds). Drone fly larvae are thus usually in polluted (nutrient rich) waters. They writhe from plants to pond bottom and back in my pond. Unlike other flies, these flies do not sting, bite, or otherwise cause problems for humans. In fact, adults look like honeybees and pollinate flowers. My batch was in the pond from about late September to mid-November. They were hardy, surviving a number of shallow freezes. One species of drone fly is Eristalis tenax whose adult is 0.5 inches and larvae 1.5 inches.
Drone-fly Larva
(Rat-tailed Maggot)
Turns into one of these