In Season 1 Episode 5 of 12 Monkeys, Jennifer is being interrogated for information. We know from a previous scene they are willing to do physical torture, but here they use, first, the threat of a rat on the face, and then second, deliberately put this insect on her chest.
We never find out what the insect is, or what it was for. Does anybody know?
Here's the scene (you see it at 1:38 min):
It's not an insect, it's an arachnid. To be more exact, it belongs to the arachnid order amblypygi, also known as whip spiders or tailless whip scorpions (not to be confused with whip scorpions).
They have these characteristic long pedipalps, but unlike whip scorpions, no tail. Here's a picture from wikipedia, taken by Thomas Brown and uploaded by mgiganteus.
If you conduct a google image search, you'll find many more pictures, e. g.
(I can't embed them directly due to copyright issues).
As for why they did that - probably to scare her into revealing the information. They look unusual and scary, especially the pedipalps. They are also relatively large for an invertebrate, but they are actually harmless to humans (see the wikipedia article).
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