Re: Can this be a laying worker?
Hi BMAC, it does rarely happen that a package will be installed and have laying workers almost immediately. Rare, but it happens.
I think the explanation must be that the package has been taken from a hive with laying workers and this was not noticed at the time. This can and does happen because many package producers do not find the queen, they put an excluder on top of the hive, then a box with a few combs, then smoke the bees up and the box, now full of bees, is taken off and shaken into packages. Of course, there is every likelihood that a package with laying workers would kill the caged queen given them and continue with the laying workers.
As you rightly surmised, whether this happened, or whether the queen given them didn't take so they got laying workers later, can be determined by the age of the larvae.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).