Vanessa Alarcon, a university student who was working at an anti-war rally in the American capital last month, told the Washington Post: "I heard someone say, 'Oh my God, look at those.'
"I look up and I'm like, 'What the hell is that?'. They looked like dragonflies or little helicopters. But I mean, those are not insects."
Bernard Crane, a lawyer who was at the same event, said he had "never seen anything like it in my life". He added: "They were large for dragonflies. I thought, 'Is that mechanical or is that alive?'"