This year when I've been out and about I've heard what I think was two different swarms on different properties. Couldn't find them before the noise went away, but it sounded like a bazillion teeny tiny drones. Soft at first, then louder, then softer, then gone.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).