Larvae predatory, adults of most species (perhaps) do not feed. Adults of a few exotic spp. are said to take blood(1)
Larvae are filter feeders or predators (using modified prehensileantennae) in shallow stagnant waters. Larvae of Chaoborus, at least, are nearly transparent and planktonic (living in water column), not associated with a substrate like most fly larvae(4). Mochlonyx larva:
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