Conrad Sigona wrote:
 
> - the "pupae" are white;
> - they are not soft like larvae;
 
 Sounds like chalkbrood. The bees should clean them out of the cells.
See if there are any in front of the hive. They look like mummified
larva and are hard. They can also be yellow and have black. If they are
there then it is a sure indicator of chalkbrood.
It is generally known as a stress disease and will usually go away
unless the hive is heavily infected which yours does not sound like it
is. Some people re-queen, but it is very common with migratory
beekeepers who live with it.
Bill Truesdell
Bath, ME