The Pentagon's defence scientists want to create an army of cyber-insects that can be remotely controlled to check out explosives and send transmissions.
Scientists who spoke to the BBC news website were unconvinced.
Entomology expert Dr George McGavin of the Oxford University Museum of Natural History said the idea appeared "ludicrous".
Darpa's previous experiments to get bees and wasps to detect the smell of explosives foundered when their "instinctive behaviours for feeding and mating... prevented them from performing reliably", it said.