the saddest, scariest, disturbing scene in film history?

Quite possibly, yes

I wouldn't go so far as to say that it's the saddest scene in history, but it's definitely disturbing. (especially since those guys don't "help him" until it's too late.)

Yeah baby! Wooooooo! Fire!

I agree, the fly in the spider's web is horrifying yet VERY VERY sad...especially what the poor wife goes through trying to FIND it, and now it's too late. I think this scene is "nightmare material".

That particular scene was indeed quite sad and upsetting. Those pathetic cries of "Help me! Help me!" are impossible to forget.

"We're all part Shatner/And part James Dean/Part Warren Oates/And Steven McQueen"

I have a multi-page article on the film and that "Help me" scene David Hedison says he was most disappointed with. He had done principle photography and was on his way to Europe to film a movie when he got the call that additional audio was needed for the film. He went to a studio in New York where he was on a layover. He went to the studio to record the "help mes" for that scene and he said he really put a lot into it, really using his voice instead of his body to act. He said when he saw the final product and how the studio accelerated the voice in that scene, he was apalled. He hated it.

In the scene where the fly was in the web and the spider was coming toward it, according to this article, both Vincent Price and Herbert Marshall couldn't keep it together. The both of them kept cracking up. They had to do several takes in order to get a copy worth putting into the film. The director, Kurt Neumann really had to cut carefully because even in the completed film, you can still see that Price and Marshall were still having difficulties keeping it together.

One interesting sidenote to it. In the article, David Hedison said the film really wasn't his or Vincent's. It was Patricia Owens' film. He said before there was a Ripley (Sigourney Weaver) there was Helene Delombre. He said really the film belongs to Patricia. I really came away from that article with a respect for David Hedison in how he wanted Patricia to get the due she was dserved. I agree.

I'd have to say the scene that scared me more wasn't the web/fly/spider scene, rather, the scenes where we see Andre as the combined fly/Dandelo/Andre being beginning to lose it. David Hedison said in the article I quoted that he played it as that Andre was really a chimera of three distinct beings. He was part fly, part Andre and part cat...remember when Dandelo was caught in the matrix? David said he incorporated that into his performance. It truly was a great read.

"Sometimes my ruminations are too confusing for someone not inside my head." -Anon

It's a classic scene from a classis movie.
And it's a freaky scene from a freaky movie.

You're gonna die!

probably that break in cinema history between a happy end and happy ever after ending..

All three of those adjectives are appropriate at once. That scene is etched in my memory, and I saw the movie 30+ years ago. I kept thinking that, as Andre become more fly-like, the fly became more human.

"I love corn!"