You think, "Spider Queen eh, that's a job i could go for..." and then suddenly, you start to change. Your mouth becomes tight as a pair of mandiblespushes out of your mouth. You try to speak but all that comes out is a strangled hiss.
You feel your ass start to swell. In seconds it bursts through your jeans, reavealing that it has become a giant, bulbous chitinous mass, extending beyong your body. Then, your legs begin to get hairy, and start to extend. they get about 4 1/2 feet long before 4 others sprout from your hips, which add to your midsection which is now clearly a thorax.
You now appear to have a woman's torso and arms, with the body of a giant spider...