When I have two firefly hives I am unable to actually get two whole swarms. I am usually unable to get even one whole swarm at one of them and I have never seen two whole swarms at the same time. Now that I'm curating the Barnacles & Fireflies Resource Route I'm noticing it on other people's streets too.
I asked around in general: Multiple firefly hives, are yours working?
and other people seem to be seeing this too. I decided to test this in my back yard. I started with one healthy happy hive at one end of the yard and added a new one at the far left. Here's how their populations varied:
I logged out after adding the 2nd hive & came back a while later to
0 L, 10 R ... then I harvested the right hive to
0 L, 3 R ... waited 5 minutes
3 L, 7 R ... (looks promising). waited 5 more minutes
3 L, 7 R ... waited 5 more minutes. still
3 L, 7 R ... harvested again to
3 L, 0 R ... waited 5 min
6 L, 4 R ... waited 5 min
6 L, 4 R ... waited 10 min
6 L, 4 R. ... then I logged out for 20 min and came back to
6 L, 4 R.
I have seen these relatively low firefly populations in every street I have visited with more than one hive. Do we have a limit of 10 fireflies/area in the "residential district," regardless of the number of hives cultivated?