A came across some bumblebees this morning doing a salvage operation.
The plant they were on is a cattail, which had been growing on the edge of a slowly drying pond until it received significant damage from an unwitnessed event. Cattails produce wind-dispersed seeds on a long stalk. The plants are perrenial and the plant typically regrows from a root each year. The root has been reported to have been a food source for the people who occupied this land before we did.
The bees are finding a sugary sap or maybe crystalized sugar in what remains of the stalk. The process is similar to the way sugar or molasses or cane sugar is produced.
Even the dried stalk seems to be attractive to them.