Abdomen/ovipositor spasms post-mortem

Today I found a female ichneumonid on the side of the road. She was clearly dead but after holding her for a while during my walk home her abdomen intermittently flexed, causing her ovipositor (which was a notable 3.5 inches) to move. Is this due to residual nerve firing and/or muscle spasms? I'm interested to know more about this.

Also, yes, I am quite sure she was dead (or at least "brain dead") as her legs were completely curled and stiffened and her antennae were immobile/stiff even when touched. She showed no signs of life besides the random flexing.