Hunt Trek

Riddle: On a certain planet located in one of the outer spiral arms of the Milky Way Galaxy, three life forms are seeking to capture other life forms and incarcerate them in glass prisons. The authorities on this planet have allowed such imprisonments for hundreds of years, despite the fact many of the captured life forms often die within 24 hours of their confinement, either by being accidentally crushed to death or by suffocation, as some of the prison cells do not have proper ventilation to supply needed oxygen to the prisoners. On this planet, hunting for these living creatures takes place after dark. The three hunters mentioned above do not follow any tracks to find their quarry, but instead, rely on these creatures to expose themselves, which they do by emitting short bursts of light. If it wasn't for the Prime Directive, I'm certain Captain Kirk, Mr. Spock, or the Federation of Planets would have put an end to this barbaric practice of hunting and imprisoning these life forms long ago. By the way, what form of life were the three hoping to capture?