Relaxing

by Andreas Herrmann

Acetic acid works quite well, but where the proteins of the muscles have become hard due to denaturation, acetic acid will not relax specimens. In such cases, a chemical is needed which will break down the proteins. In Germany we use simulated gastric juice for this aim: 1% pepsin, 1% hydrochloric acid and 98% water. The solution (as well as the pepsin powder itself) should be stored at temperatures below 15 °C when not in use.

I use the same glass tubes (10 or 20 ml) as for killing specimens. Put a few beetles into a tube and fill it with pepsin solution. Then store in a warm place such as an airing cupboard or above a radiator (maybe at 30 or 40 °C) and leave for a few days. If the beetles are still stiff after a few days, they can be left for up to a few weeks but I rarely have to do this. More time is needed for larger beetles, or at lower temperatures. Discard the pepsin solution afterwards: it can only be used once.


3 Comments

  1. johan says:

    Hello,

    This seems an ideal solution but having spent most of the morning phoning round and googling I can’t seem to get hold of pepsin powder. This would help me a lot as I do photography of specimens – see the link.

    I am not much of a chemist – can anyone confirm that digestive aid vitamins containing pepsin and betaine HCL, dissolved in water, might have much the same effect?

    Many thanks for your time

    -Johan
    ingleslenobel-at-internet-dot-com

  2. markgtelfer says:

    Johan,
    I recommend you ask Andreas Herrmann (http://www.dermestidae.com/). Please let me know the answer.
    Thanks,
    Mark

  3. Ian McClenaghan says:

    A long time ago a Japanese entomologist published in the AES bulletin that you could use the proteolytic enzyme in fig juice to relax insects. I have never tried it.

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