This is how some insects overwinter, protected from the winter elements and predators, until the following spring. When you open routered nesting tunnels or Beediverse Corn nesting trays, you may find all kinds of insects using the nesting tunnels.
The top row consists of leaf cutter bee cocoons. It is difficult to see the individual compartments each containing a cocoon. Leaf pieces tend to overlap from one cell to another. Different shades of green probably means that pieces were chewed off from different species of plants.
The mid row contains pupae of the resin bee. Resin bees use tree resin as cell liners and dividers. The bee larvae feeds during the summer months, until it grows into a pupae. This little yellow ‘grub’ overwinters in this life stage form until warm temperatures allow it to develop into an adult bees.
The 3rd and lowest nesting tunnel contains the mason bee or the spring mason bees Osmia lignaria. It uses mud to make its compartments- save from predators and the weather.
All three insects are pollinators. Leaf cutter bees and Resin bees generally pollinate during the summer months, whereas Mason bees pollinate in the early spring.
When opening nesting tunnels, I return the nesting trays to their housing with the resin bee pupae and leaf cutter bee cocoons intact. I remove the mason bee cocoons, and process them. Processing these cocoons means removing the mud and any mites that may be attached to them.