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MIT builds swarms of tiny robotic insect drones that can fly 100 times longer than previous designs
(www.livescience.com)
This is a most excellent place for technology news and articles.
Looks like they hovered for 1000 seconds. It was previously stress limited such that the joints would break after just a few seconds. I think they might still be tethered for a power source, I haven't seen any of these micro flapping bots include a battery yet, and they didn't mention that they did.
https://www.science.org/doi/10.1126/scirobotics.adp4256