What do mason bee cocoons look like inside the nest?

These cocoons were harvested early October just when weather was getting colder
and water was condensing on the Quicklock nesting trays.
Early enough to  avoid fungal growth over cocoons.

These cocoons were harvested in early Nov, after cold weather had settled in.
A few cocoons were covered in mold.  This mold is easily washed off in cold water and a little bleach.
Quicklock nesting trays with 4 healthy looking cocoons.
Cocoons are covered in feces which is easily washed off in cold water.
Quicklock trays with healthy cocoons.  The brown and black speckles
are bee feces or frass.
Frass is easily washed off in cold water.

These are different coloured mason bee mud plugs in Quicklock nesting trays.
The black paint is used to help bees orient to their nesting tunnel.

Small cocoons towards the front of the tunnel are usually males.
The females are in the back of the nesting tunnel and are larger than the male cocoon.
Sometimes a nesting tunnel consists of a few mud debris.
The female either died before she could finish the nest or she  became
 disoriented and found another nesting tunnel for nesting.
Tunnels can be completely full or partly filled.