Hibernaculum !

Hibernaculum  - Latin term for winter quarters, The official term used to describe a variety of shelters used by many kinds of animals, including insects, toads, lizards, snakes, bats, rodents, and primates of various species.

I came across this one in the 'cordite store' at Rainham RSPB, one of many scattered across the reserve, affectionately referred to as a 'the Invertebrate Palace'

This one constructed not only to provide a year round home for insects and spiders, but also for Yellow Necked mice, lizards and grass Snakes.

To be perfectly honest, I have never seen a creature anywhere near one of these shelters, but on this occasion I noticed a few Bees flying around the front of the structure, so I decided to watch these from a conveniently placed bench next to the shelter.
 I was in for a pleasant surprise as a number of Bees were using the Hibernaculum, some I could recognise, some remain a mystery.

So I will start with an easy one which I hope I have correctly identified, and that is the Leaf -Cutter Bee Megachile centuncularis . slightly smaller than a Honey Bee, the abdomen all black, the underside being bright orange.
In the time I watched these coming and going, not once did one arrive carrying a piece of cut leaf which was disappointing. But nice to see the Bees using the hollow tubes.

I can not positively identify this one, my first thought was that it was possibly a male Leaf-Cutter but dos'nt seem to fit the description in my Bee guides, nice looking Bee though but shall remain one of those mystery's unless someone can identify for me.

Another easy one to identify was this Ruby Tailed wasp, only the second that I have ever come across. Appropriately for a 'cuckoo wasp' this one was inspecting the cavities in the old bricks placed in the hibernaculum looking for a host nest to place its egg I suspect.

Here's another unidentified  resident of the palace

A bad photograph of another tiny black wasp like resident, probably another parasitic type wasp which was seen investigating the hollow tubes.

Contrarily to my first impression of  no life here, there was plenty to see, you just need to sit quietly and watch to see what turns up. I do not think I will pass one of these structures now without taking a closer look in future.