A question about beetle mandibles

[777]

I have recently pinned a Mallodon dasystomus found in an old vial of alcohol. I wanted to display the beetle with its formidable mandibles open, but I could not open them despite the insect being entirely flexible. Is there any trick to combat this, or do I just have to deal with it? 

[billg]

I take a fine paintbrush and get wet with gin. Then seep the fluid into the joint where the mandible meets the head. Do this several times and wait a few minutes each time. Then gently work it with your fingers to loosen/free it. If not successful, repeat until it works. I’ve loosened many large stuck mandibles this way when the rest of the beetle was softened. It takes patience, but is better than breaking it. Since the beetle was in alcohol, you may have an issue that may cause this method to not work. The bugs I did it with were not stored in alcohol. Good luck.....it’s worth a try. The gin is the kind one drinks and I use a dry gin.

[trehopr1]

Sometimes the mandibles and even the entire head capsule can be problematic with beetles. When stored in alcohol (and especially anything more than 70% alcohol); mandibles can "lock-up" and heads can remain "turned" or crooked seemingly never to be straightened. Try out billg's idea or you could try dipping the entire head into a measuring cup of pre-heated hot water for 20-30 seconds. Then try to either turn the head or part the mandibles with your fingertips.
Use firm pressure but, nothing too much and things should work. However,if not and you do not sense any change (don't push your luck) and accept that you may have to leave well enough alone or you may pop off a head or bust off a mandible.
I have a couple beetles that simply resisted me to no end and I had to "throw in the towel" on my efforts or I might have otherwise damaged them irrevocably .

[777]

Thank you all for the advice!

[777]

Jan 15, 2019 6:51:40 GMT trehopr1 said:

Sometimes the mandibles and even the entire head capsule can be problematic with beetles. When stored in alcohol (and especially anything more than 70% alcohol); mandibles can "lock-up" and heads can remain "turned" or crooked seemingly never to be straightened. Try out billg's idea or you could try dipping the entire head into a measuring cup of pre-heated hot water for 20-30 seconds. Then try to either turn the head or part the mandibles with your fingertips.
Use firm pressure but, nothing too much and things should work. However,if not and you do not sense any change (don't push your luck) and accept that you may have to leave well enough alone or you may pop off a head or bust off a mandible.
I have a couple beetles that simply resisted me to no end and I had to "throw in the towel" on my efforts or I might have otherwise damaged them irrevocably .

Your advice worked! After dipping my specimen, its jaws popped right open! Again, I thank you. I will use this technique again for any future "locked" beetles.