Absolutely because if the trap isn't emptied it becomes a low efficiency trap allowing wasps to enter, feed and escape to recruit more wasps to the vicinity of the trap. Not a problem so long as users understand the need to monitor such traps carefully and maintain them accordingly to sustain the higher level of efficiency as when first baited up when empty. Their capacity is circa 200 to 300 wasps. Not a large number when used around apiaries (possibly as little as a day's worth of capacity where wasp pressure is high) so need to be used with all of the requisite caveats.