The swarm 50ft up a tree may be moved down to a much lower branch,
from which they can then be conveniently dropped off into whatever box you
plan, by shining a very bright light as a spot on the top of the swarm.
Given a clear sun and lucky geometry, you can use a hand mirror, which I
have found to work a treat (tho' does take perhaps 10min).
        I haven't tried this with an artificial light.  Whether it's the
light or heat or both I have no idea.  It is only about 50W of visible plus
IR so I doubt it can do serious harm.
         Several friends have also done this.  The method seems to be
fairly widely known in New Zealand; I don't know about elsewhere.  It is
for some reason quite fun  -  the fluid glob moves steadily downward by
remote control.   Gives you that Overlord feeling, perhaps.
        But then, I like swarms in many ways.

R