None of the night's events have made sense, but there must be an explanation to all of this. With that, you quickly slip on a pair of pants (a tight fit with your latex protrusion) and go back out to search for clues. Of course, there's only one place you could start.
As you arrive at that streetlight you see the scene exactly as you left it, the rainbow of latex puddles still shining from the light above them. You begin to approach them, but as you do they begin to shudder, almost as though they were restless. You back away; the shuddering stops. Every motion you make towards them seems to make them shake. Is it that they sense you, or... no. No, it's not you they sense. It's the part of them attached to you.
You try moving in even closer this time. The puddles seem to be shivering violently now, surges of motion pulsing through them. Even more interesting, however, is that the latex on your backside has begun to quiver. It seems anxious to join its brethren (or perhaps they wish to join it). You contemplate for a moment whether you should risk getting closer, but you know you have no choice if you want answers.
Once you're within a meter of the substance, the shivering becomes a more steady wiggle. Each puddle seems to join in a synchronized flow, gathering in a pool that inches its way towards you. As it does, the latex in your pants begins pushing to escape. You gladly drop them to let it out and it enters the pool, which is now entirely jet black aside from the highlights of reflected light on its surface, and the motion stops. Now that you're latex-free, you can just pull up your pants and leave this all behind you.