I saw some about 8PM today, so "glitch" is looking less likely! They seem to be very sporadic - I saw five or so in a span of fifteen minutes, but didn't see any at all last night. Someone in the discussion thread on the DC forums was complaining that they'd picked up eggs from three different biomes but they all looked the same, was that a glitch? But it was the "flow" eggs. So apparently they hit all the biomes, but there may be some kind of mechanism at work as to when they appear....