I understand that it would be downright ungentlemanly of me to celebrate Mrs. Ivan's discomfiture. At the same time, it's difficult for me to apologize with any sincerity between fits of giggling.
My better instincts tell me I ought to make nice, so...
Please, Mrs. Ivan, I'm sorry. I won't do that to you again.
No worries (but don't laugh too much).
Around spiders I am a wimp, especially large, scary, unexpected spiders.