Catch, capture, trap, snare, entrap, ensnare, bag are comparable when meaning to get into one's possession or under one's control either by taking or seizing or by means of skill, craft, or trickery.
Catch, the ordinary and general term of this group, distinctively implies that the thing laid hold of has been in flight, in concealment, or in constant movement and that possession has been gained by pursuit, force, strategy, or surprise or by means of a device or accident which brings it within one's reach physically, visually, or mentally.
Sometimes the power of laying hold of is ascribed not to a person, his vision or other sense, or his mind, heart, or imagination but to the thing which draws to itself his attention, his eye, or his fancy.
Capture implies heavier odds (as greater opposition or difficulty or more competition) than does catch and suggests a taking possession that amounts to an overcoming or a victory.
Trap, snare, entrap, and ensnare imply catching by a device which holds the one caught in a position that is fraught with danger or difficulty or from which escape is difficult or impossible.
Trap and snare imply the use of a trap or snare (see LURE n), but entrap and ensnare suggest trickery in capture more often than the use of an actual trap or snare: all four terms impute craft to the catcher and unwariness or lack of caution to the one that is caught. Distinctively, trap and entrap suggest a being held in a position where one is at the mercy of the captor and his designs, and snare and ensnare a being held so that the more one struggles the more desperate becomes one's situation.
Bag carried a double implication of catching (as game or specimens) and of putting into a container (as a game bag) for transportation or storage.
So strong is the implication of catching and killing game in this use that the word is often employed without suggestion of putting in a bag.