The theft of over 1,000 Hebridean black bees from a garden in Scalpay was reported to police late on Monday night (August 27th).
The incident is the second in the area in less than 18 months, with two hives stolen from Manish in Harris in April 2017.
The latest theft happened between 15th and 23rd August, while the owner was away.
Police said the thieves needed specialist skills and equipment, but were also likely to have known that the bees were not supervised at that time.
The bees, Apis mellifera mellifera are becoming increasingly rare and are the only native honeybee species.
Colonsay and Oronsay have been designated as reserves to maintain a population free from cross-breeding with other non-native species.
Western Isles police are asking for anyone who can provide any information to contact them, using the non-emergency number 101.