Medium to large butterflies can be safely handled and released by persons who know how to do it. Any butterfly can be fatally damaged by being handled improperly. For example, the vein on the front wing if broken will cause the butterfly to be flightless evermore. Their internal organs can be injured. Although the loss of some wing scales does not harm the butterfly, many folks prefer not to see butterflies in butterfly conservatories with thumb prints on their wings.
Handling a Lorquin's Admiral (Limenitis lorquini)
Gently holding a swallowtail