It's not so much that they eat it but rather they remove it from the hive. the act of them removing it causes the oil to be spread around on bees. how these extender patties are thought to work is therorized in 2 ways in 1) It causes the hairs on the bees to get stiff preventing access to the trachea and 2) prevents the mites from finding a host by masking the young bees pheromones that the mites use to distinguish between young bees and older bees and thus limiting their reproduction.
this treatment was discover by accident when researchers were attemting tests on bees for TM treatments. The bees were kept in jars vaseline on the inside of the rim, those bees showed less mites then the others regardless test treatments or no treatment. it was soon discovered that the vaseline was the common denominator. that was back in the early 90's
Will Gruenwald Chilliwack BC