Mailing of the butterflies

Such a container should be packed in another, larger one (at least in a mailbox) and the gap between the walls of the container and the box should be filled with amortizing material. Then the chances increase significantly.

As for the shock-absorbing material inside, I didn't find any options

ready to be a test subject, you can send me some interesting pigeons and fatheads and other butterflies

The simplest is cotton wool

I do not think that cotton wool will help, rather, on the contrary, the antennae and paws will cling to it, and most likely the straightened butterfly will not be untangled from it without loss. But once again I repeat the experiment everything is a head

No, the cotton wool should be outside the foam "container", between it and the walls of the mailbox.

It's hard for me to imagine what you need to do with a parcel to make a steel or plastic container fall apart, but the fact is the fact.

I saw at the local post office, as receiving parcels, they were thrown from a height of two meters on the concrete floor.

The straightened butterfly was thrown from such a container to the floor from a height of one and a half meters - without damage. If packed in bubble wrap, it should reach. We should try to send to whom thread what thread.

It seems to me that switching to EMS or a similar mailer is still inevitable. The last few years have shown the amazing ability of our mail to crush any container to smithereens. I can hardly imagine what you need to do with a parcel to make a steel or plastic container fall apart, but the fact is.