Modpack: FTB Revelations 2.5.0
(Newest is 2.6.0, and due to the nature of the issue, I can't really test it out right away in the new version)
Forestry version 5.8.1.322
Binnies version: 2.5.0.168

Image and Title tell it all. After leaving the server running for about 2 weeks, I came back to about 1300 butterflies, dragging the tickrate from 30ms to well over 70ms.

A good portion of them seem to be stuck in chunks that aren't actually chunkloaded. A possibility is that they are wandering into an unloaded chunk and living forever there until the chunk is loaded again, causing them to slowly accumulate over time. (I killed them with commands, in retrospect I should have waited to see if they would eventually all die off if the chunk was loaded

If my hunch is correct, this isn't much of a major issue, as active users on a server should leave no unloaded chunks for butterflies to wander into