I’ve seen at least one video of a fly or housefly that seemingly pulled its own head off when grooming. (I do suspect that the head / neck was probably damaged by something else, first)

Then the fly flies off and goes about its day. From what I understand, they can actually live for a while like that, if in a bumbling sort of way. But with no way of absorbing moisture & nutrition, they do die prematurely.

You might be interested in learning about Mike the headless chicken, who lived for 18mos after being beheaded:

https://en.wikipedia.org/wiki/Mike_the_Headless_Chicken

Interesting subject, but I couldn’t read enough of the article it find out what’s going on. Probably poorly translated; slop usually at least has correct sentence structures.